Stainless Steel Compression Coupling Fittings for Pipe — 4mm to 16mm

Match the fitting size to your pipe's outer diameter (OD) — not the nominal pipe size. For example, a 4mm fitting suits tubing with a 4mm OD (approximately 5/32"). Use calipers to measure your pipe OD before ordering. Available sizes range from 4mm (≈5/32") to 16mm (≈5/8"). When in doubt, size up and verify — a fitting that's too small won't seat properly.

Stainless steel compression fittings generally handle working pressures up to 150–300 PSI, though the actual rating depends on the pipe size, wall thickness, and the tubing material being used. For critical or high-pressure applications, contact us to confirm the rating for your specific size and use case before installation.

Yes. Stainless steel provides strong resistance to rust, oxidation, and mild chemical exposure, making these compression couplings well-suited for outdoor irrigation systems, exposed plumbing runs, humid crawl spaces, and coastal environments where standard carbon steel or brass fittings may corrode over time.

These fittings are typically compatible with copper, soft copper, nylon, and polyethylene (PE) tubing of matching outer diameter. They are not generally recommended for rigid PVC or CPVC pipe without a liner insert, as rigid plastic may not compress evenly under the ferrule. Contact us if you're working with specialty tubing materials.

In most cases, only two adjustable wrenches are needed — one to hold the fitting body steady and one to tighten the compression nut. No soldering torch, crimping tool, or pipe threading equipment is required. This makes compression couplings one of the most DIY-friendly pipe connection methods available for small-bore tubing repairs.

One compression coupling connects two pipe ends, so you need 1 piece per joint. If you're repairing a section of pipe, you'll typically need 2 couplings (one at each cut end) plus a replacement pipe segment. Order in bulk (5, 10, 20, or 50 pcs) if you have multiple joints to connect — bulk packs offer a lower per-unit cost.

These are compression-style fittings that use a ferrule-and-nut mechanism rather than a threaded pipe connection, so no NPT or BSP thread standard applies to the pipe end itself. The compression nut is typically metric-threaded to match the fitting body. If you need to connect to a threaded port or adapter, contact us to confirm compatibility before ordering.