Boss Plugs | McMaster-Carr

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388 Products

About Pipe and Fittings

Measure your pipe and fittings to identify their pipe size, thread size, schedule, and thread type. Then, find compatible components.

Metal Pipe and Pipe Fittings

Compact Extreme-Pressure
Steel Threaded Pipe Fittings

These fittings are strong enough to handle extreme pressures, yet small enough to fit into cramped spaces.

Extreme-Pressure Steel Threaded Pipe Fittings

The strongest steel fittings we offer, these can withstand extreme-pressure applications.

High-Pressure Galvanized
Steel Threaded Pipe Fittings

A galvanized finish gives these fittings better corrosion resistance than our plain steel high-pressure fittings. Also known as Pressure Class 3000 fittings.

High-Pressure Steel Threaded
Pipe Cap and Plug Assortments

The heavy duty caps and plugs in these assortments come in various sizes and stand up to high-pressure flow applications. Made of steel, they’re for use in noncorrosive environments.

High-Pressure Iron and Steel Threaded Pipe Fittings

These fittings can stand up to high-pressure applications. Use them in noncorrosive environments.

Low-Pressure Iron and Steel Threaded Pipe Fittings

Use these fittings for low-pressure applications in noncorrosive environments.

Extreme-Pressure Stainless
Steel Threaded Pipe Fittings

Use these fittings in extreme-pressure conditions up to 15,000 psi.

High-Pressure Stainless
Steel Threaded Pipe Fittings

Use these heavy duty, corrosion-resistant fittings in high-pressure flow applications.

Medium-Pressure Stainless
Steel Threaded Pipe Fittings

Choose these fittings when you want the same high-quality found in our low-pressure pipe fittings, but need more strength to handle higher pressures.

Miniature Medium-Pressure Stainless
Steel Threaded Pipe Fittings

When space is at a premium choose these compact fittings.

Low-Pressure Stainless Steel Threaded Pipe Fittings

Use these corrosion-resistant fittings in a low-pressure pipe line.

Premium Low-Pressure Stainless Steel
Threaded Pipe Fittings with Certification

Unlike other stainless steel fittings, these are made in the U.S.A. for superior quality. As another marker of quality, they come with a certificate with a traceable lot number and test report that guarantees material composition.

Miniature Low-Pressure
Brass Threaded Pipe Fittings

Less than an inch in length, these miniature fittings work well in low-pressure pipe lines that are tight on space.

Low-Pressure Aluminum Threaded Pipe Fittings

In addition to being lightweight, these aluminum fittings offer good corrosion resistance. Use them in low-pressure flow applications.

High-Pressure Aluminum Threaded Pipe Fittings

Also known as Pressure Class 3000 fittings, these have the highest pressure rating of all the aluminum pipe fittings we offer.

Medium-Pressure Aluminum Threaded Pipe Fittings

Designed for medium-pressure applications, these fittings have better strength than our low-pressure aluminum pipe fittings.

Titanium Threaded Pipe Fittings

Titanium has similar strength to steel, but is approximately 40% lighter. It has better corrosion resistance than most stainless steel alloys and can handle corrosive substances, such as salt water and acids.

Quick-Disconnect Hose Couplings for Pressure Testing

Quick-Disconnect Hose
Couplings for Pressure Testing

Add quick connection points for mechanical gauges and other diagnostic equipment to your line. These couplings are also known as test ports and diagnostic couplings.

Metal Pipe and Pipe Fittings

Compact Extreme-PressureSteel Threaded Pipe Fittings

Extreme-Pressure Steel Threaded Pipe Fittings

High-Pressure GalvanizedSteel Threaded Pipe Fittings

High-Pressure Steel ThreadedPipe Cap and Plug Assortments