How to find an OEM number on a brake or clutch part

Where the number is stamped, how the main makers format it, and how to tell an OEM number from an interchange number.

Most brake and clutch parts carry their number somewhere on the body, but the marking is often faint, painted over, or hidden under dirt and brake fluid residue. This guide covers where to look and how to read what you find.

Where the number usually is

• Cast body — raised or engraved on the side of the cylinder barrel, often near the flange. Clean the area and use side light, not direct light.
• Reservoir cap — some makers put the assembly number on the cap rather than the body.
• Paper or laser label — on the body for aftermarket parts, sometimes only on the box.
• Piston / pushrod end — bore size is sometimes stamped here instead of the part number.
• Clutch slave and release bearing — number is usually on the housing face or the bearing collar.

How the main makers format numbers

OEM number versus interchange number

An OEM number is what the vehicle maker assigns. An interchange number is what a brake manufacturer assigns to the same physical part — TRW, Bosch, Aisin and others each use their own system. Both identify the part, and a good catalogue cross-references them. When you quote, send whichever number you have; the fewer characters you guess, the faster the answer.

Beware of numbers that look similar but differ in one character. 47201-26821 and 47201-26811 are different assemblies even though both exist for the same vehicle family. Always copy the number from the part itself rather than from memory.

Searching this site

Every product page here is keyed on the OEM number, and each page lists the interchangeable numbers we hold for that part. Paste any of them into the search box on the products page — the page will open even if the number you have is the second or third reference.