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When you’re adding an oxygen sensor to a header, downpipe, or straight-pipe build, you need a clean, leak-free weld point for the sensor to thread into—and a plug to cap off any port you’re not using. The right kit delivers both without stripped threads or a galling plug.
I’m Min — the founder and writer behind Gadgets Feed. This guide is built by comparing the manufacturers’ published specifications and the patterns across verified customer reviews, so you get each pick’s real strengths and trade-offs instead of marketing spin.
Whether you are welding in a bung for a wideband gauge or sealing an unused port, this o2 sensor plug roundup separates the truly leak-proof kits from the ones that will frustrate you.
Our Picks at a Glance
How To Choose The Best O2 Sensor Plug Kit
Before you buy, you need to know what you are actually capping or adding. An O2 sensor bung is the threaded collar you weld into the exhaust pipe, and the plug is the solid cap you screw in when you do not want a sensor in that port. Most kits bundle both, but the material and design decide how long they last under extreme heat.
Match the Thread Pitch to Your Sensor
The standard thread size for almost every oxygen sensor is M18 x 1.5—an 18-millimeter diameter with a 1.5-millimeter pitch. Every kit in this list uses that same pitch, so any of these bungs will accept a standard Bosch, Denso, or NTK sensor without adapters. If you are capping a factory port that never had a sensor, measure the thread before you order—confirming your fit first saves a return trip.
Material Choice: Stainless vs. Mild Steel vs. Zinc
304 stainless steel resists corrosion in harsh environments and welds cleanly without deforming, which is why most aftermarket kits use it. Mild steel versions are cheaper and easier for some hobby welders to fuse, but they will not match the longevity of stainless. Zinc-plated plugs are a different story—they are meant for sealing a factory Harley-Davidson port, not for welding into a custom pipe, so match the material to the job you are doing.
Stepped vs. Straight Bung Design
A stepped bung has a shoulder that sits flush against the pipe, giving a clean look and an easier weld bead to lay down. A straight bung is simpler but requires more skill to position and weld at the right angle. If you are new to welding, the stepped design is the more forgiving choice for a professional-looking finish.
Quick Comparison
| Model | Best For | Material | Pieces | Pipe Fit | Amazon |
|---|---|---|---|---|---|
| JGR Stepped Weld Bungs★ Best Overall | Budget-minded custom builds | Alloy Steel | 10 | Universal | Amazon |
| HOHNNYREET 4-PackTop Performer | Top-rated small jobs | 304 Stainless | 4 | Universal | Amazon |
| HYAT Bung & Plug Set | 1.5–2.5 inch pipes | 304 Stainless | 4 | 1.5–2 in | Amazon |
| joytrace Weld Kit | TIG welding into headers | Stainless Steel | 5 | Universal | Amazon |
| HOHNNYREET 6-Set | Multi-port projects | 304 Stainless | 12 | Universal | Amazon |
| Vance & Hines Plug Kit | Harley-Davidson OEM ports | Zinc | 2 | 18mm ports | Amazon |
In‑Depth Reviews
1. JGR O2 Oxygen Sensor Stepped Weld Bungs (5 Bungs/5 Plugs)
Our pick — over 4.5★ from 450+ verified ratings; the strongest balance of quality and price.
Ten pieces of weld-ready port hardware that covers a whole custom exhaust project in one box.
This is the kit you grab when you are building an exhaust from scratch and need both bungs and plugs in quantity. You get 5 bungs and 5 plugs machined to the standard M18 x 1.5 thread, so every piece in the box fits a universal oxygen sensor without adapters. The boss and the plug share that same thread, which makes planning easy when you are laying out sensor locations on headers or downpipes.
Buyers report the material welds easily and the threads are well done, with one noting it was the right product for the job done the same day it arrived. Rated for 1500 °F, this alloy steel build is meant for the heat of an exhaust system, and the stepped design sits flush for a cleaner bead. The trade-off is the material—it is alloy steel, not stainless, so it cannot match the corrosion resistance of the higher-priced kits here.
With 10 pieces for a modest outlay, this is the value play for anyone who wants spares on hand without paying per-part prices. If your project runs to multiple sensors and you want to avoid a second order, this is the one that covers you.
What the Box Gives You
- 10 total pieces—5 bungs and 5 plugs—for one low-cost buy
- Rated to 1500 °F so it is built for exhaust heat
- Welders praise the easy-to-weld alloy and clean threads
Where It Falls Short
- Alloy steel lacks the long-term corrosion edge of 304 stainless
- No included carrying case for storing spare pieces
Built for spares: this 10-piece set is the pick for budget builds where you want bungs and plugs for every port in one shot.
Think about corrosion: if your truck lives in a salt-belt winter, the stainless kits below will outlast this alloy steel.
2. 4 Pcs O2 Sensor Bung, 304 Stainless Steel M18x1.5
Four stainless bungs so nicely machined they arrive in a protective case you will actually keep.
This is the rare budget-adjacent kit that feels premium from the moment you open it, largely because the pieces come in a case so you will not lose them. The 304 stainless construction resists corrosion in any environment, and the stepped mounting design makes a flush weld finish manageable for both pros and DIYers. Each bung carries the standard M18-1.5 thread, so any standard oxygen sensor threads straight in.
Owners mention the part fits well, feels solid, and performs reliably, with one noting the fit and price were fantastic for the job. Unlike the alloy steel JGR set above, this one gives you the corrosion resistance of true stainless at a similar price point—just fewer pieces. The 3.2-ounce weight tells you these are machined, not cast cheaply.
The only real limit is quantity: 4 bungs and no plugs in the box. If your job needs a cap for an unused port, you will buy a plug separately.
Weld-ready: the stepped stainless build welds clean and resists rust, and the storage case keeps the spares organized.
One gap: you get 4 bungs with zero plugs, so plan for that if you need to seal a port.
3. O2 Oxygen Sensor Bung, Universal 304 Stainless M18x1.5
This kit includes two bungs (the weld-on threaded bases for your sensor) and two plugs, with a curve that fits 1.5 to 2 inch exhaust pipe—so you can cap an unused port and keep the exhaust flow smooth.
This kit earns its keep with a bung curve designed specifically for 1.5-2 inch exhaust pipes, which means the weld sits at a natural angle on common street exhausts. The 304 stainless resists rust in extreme environments and does not deform over time, and customers note it welds nicely without stripping when torquing the sensor down. One owner straight-piped a 5.7 Grand Cherokee and called the fit perfect.
The thing everyone raves about is the quality—the stainless is high-grade and takes a TIG weld beautifully. Fit ranks as a close second in owner feedback, with a buyer noting it fit his 3-inch diameter pipes with zero issues, even though the listed curve targets smaller tubing. You get 2 bungs and 2 plugs, which is the right count for a single-sensor job with a spare cap.
The one caution: the threads can gall if you weld with the plug installed, so the review pages advise pulling the plug out before you lay the bead. Do that and this kit is a smooth, leak-free install.
Proven in the field: the quality is the standout here, and the curved base makes it the easiest of the stainless sets to position on round pipe.
Watch the heat: remove the plug before welding so the threads do not gall and lock the cap in place.
4. M18x1.5 Oxygen Sensor Weld Bungs & Plugs Kit (5 Bungs/5 Plugs)
Pre-beveled edges built for TIG welding straight into headers without any pre-grinding.
This kit is designed with the welder in mind, right down to the pre-beveled edges and smooth surfaces that let you TIG or MIG weld directly without grinding first. The M18x1.5 threads are laser-cut and fit all standard sensors from Bosch, Denso, and NTK, and the tapered base is meant to stay tight under vibration in high-temperature exhaust environments. Rated to 815 °C, it is built for serious heat.
Reviewers point out welding these into exhaust headers with great results and no leaks, and one used a TIG in a differential cover with zero problems. Quality and weld quality are the two things owners praise equally, with functionality close behind. The 5-bung, 5-plug count makes it a strong value for a multi-sensor build against the 6.0x piece-count gap separating the small and large sets in this roundup.
The low-profile plug is a nice touch for tight exhaust tunnels where a bulky cap will not clear the frame. If you are welding into a header where grinding is a chore, this is the kit that removes that step entirely.
Why Welders Like It
- Pre-beveled edges save prep time before every weld
- Rated to 815 °C for high-temp exhaust use
- Fits Bosch, Denso, and NTK sensors without adapters
Worth Knowing
- Fewer total owner reviews than the more established kits
- No storage case, so keep the spares in a bag
Grab it for headers: the pre-beveled, low-profile design is the most welding-friendly kit in the lineup.
Skip if you need a case: the smaller stainless set above gives you organized storage.
5. O2 Sensor Bung and Plug 6 Set, 304 Stainless Steel M18-1.5
A dozen stainless pieces—6 bungs and 6 plugs—for builds that need multiple sensor ports capped.
This is the most complete stainless package in the list: 6 bungs and 6 plugs machined from 304 stainless with the universal M18-1.5 thread. The stepped mounting design gives a flush weld finish that suits both pros and DIYers, and the stainless corrosion resistance makes it a long-term fit for any environment. If you are building an exhaust with multiple sensor locations, this is the kit that has you covered for every port.
Shoppers say the plugs worked perfectly on a new Harley exhaust while the bung holes were used for repairs, which shows the dual role this set plays well. The quality is what owners praise most, with functionality and weld quality following close behind—one even landed a successful installation using steel flux core wire. The 6.0x count gap versus the 2-piece set above shows just how much more coverage you get here.
The only consideration is the price, which sits at the higher end of this group because you are paying for 12 machined stainless pieces. If you only need one port capped, this is more than you require.
Full coverage: 12 stainless pieces in one box is the most complete kit here, ideal for a multi-port custom exhaust.
Overkill risk: if you need a single bung, the 4-piece stainless set is the leaner buy.
6. Vance & Hines O2 Sensor Port Plug Kit – 18mm x 1.5
The factory-correct fix for pre-closed-loop Harley models running newer exhaust systems with sensor ports.
This kit exists for a very specific reason: it lets select pre-closed-loop Harley-Davidson models run newer exhaust systems that come equipped with O2 sensor ports the bike never uses. The set includes two zinc-plated, Allen-head threaded plugs with sealing washers, and you simply screw them into the nonessential sensor ports. It fits the standard 18mm x 1.5 port size used across many exhaust setups.
Buyers report it fits fine in an RPW exhaust on a Victory and works perfectly with a Dresser Dual Header setup on a 2004 Electraglide Classic that has no O2 sensor. The thing everyone notes is how easy the install is—anti-seize on the threads and a torque to spec and you are done, with functionality the most-praised aspect. The zinc plating is the right call here because these plugs are not being welded; they are sealing a threaded factory port.
The honest caveat seen in owner feedback is that the plugs feel expensive for what is essentially two caps, especially compared to the multi-piece kits in this list. For a Harley owner running new pipes, the brand-specific fit is worth it; for a custom exhaust builder, the stainless kits above give far more hardware for the money.
Built for the Job
- Zinc-plated Allen-head plugs with sealing washers included
- Trivial install—anti-seize, torque, and done
- Purpose-built for pre-closed-loop H-D models
Fair Warning
- Only 2 plugs in the kit for the highest price in this lineup
- Requires knowing whether your bike actually needs them
Made for the niche: this is the right tool for a Harley owner who bought new pipes with ports the bike does not use.
Not for custom builds: anyone welding a bung from scratch gets far more value from the stainless kits.
Understanding the Specs
M18 x 1.5 Thread Pitch
This is the universal thread size for almost every oxygen sensor on the market, which is why every kit here uses it. The 18 refers to the diameter in millimeters, and the 1.5 is the distance between thread peaks. Matching this pitch to your sensor is the difference between a leak-free seal and a stripped port.
304 Stainless vs. Alloy vs. Zinc
304 stainless resists corrosion and welds cleanly without deforming, making it the go-to for weld-in bungs. Alloy steel welds easily and handles exhaust heat but rusts sooner in harsh climates. Zinc plugs are designed for screwing into factory ports, not for welding, so they fit a different job entirely.
Stepped Bung Design
A stepped bung has a shoulder that rests flush against the pipe, creating a clean joint and a simpler weld bead. It is the more forgiving option for DIY welders because the step holds the bung at the right depth while you work. A straight bung needs more patience to position at the correct angle.
Temperature Rating
The maximum heat a bung can handle before the material degrades, measured in Fahrenheit or Celsius. Exhaust systems run hot, so a rating like 1500 °F or 815 °C tells you the part is specced for the job. A lower rating is a warning that the metal may weaken in prolonged high-heat use.
FAQ
Will an M18 x 1.5 bung fit my oxygen sensor?
Why do the threads gall when welding?
What is the difference between an O2 bung and an O2 plug?
Can I weld a stainless bung with a regular MIG welder?
Will a plug kit work on a Harley without an O2 sensor?
How many bungs do I need for a custom exhaust?
Is stainless steel better than mild steel for a bung?
Why does a plug need a sealing washer?
Final Thoughts: The Verdict
For most buyers, the o2 sensor plug winner is the HOHNNYREET 6-Set because it pairs 304 stainless durability with a complete 6-bung, 6-plug count that covers any custom exhaust job. If you want the best value per piece, grab the 4-Piece Stainless Set for small jobs. And for a Harley owner running newer pipes, the Vance & Hines Plug Kit is the one to reach for.
How We Picked
We do not accept paid placement. Every pick is matched to a real buyer and a real use-case; we do not hands-on test units.
Sources & Methodology
Specifications: manufacturer listings and product documentation. Review insights: verified customer reviews, as of August 2026. Pricing: not shown on this page (it changes often); check the current price via the retailer link.
As an Amazon Associate, Gadgets Feed earns from qualifying purchases. This does not affect which products we feature.