Toto shank assembly THP4165

THP4165 is a TOTO setscrew, a small threaded fastener used to lock a handle or trim component onto its shank. The spec is M5-6g x 15, driven with a 2.5 mm hex key. It is a replacement fastener only, not a complete handle or valve assembly.

On TOTO trim, the setscrew is the part that clamps the handle to the shank, and a stripped or missing one is the usual cause of a handle that spins or works loose. THP4165 is that replacement fastener, M5 x 15 mm with a 2.5 mm hex socket. If the socket in your existing screw is rounded out, replacing it is the fix; if the handle splines themselves are worn, the screw alone will not hold.

A 2.5 mm hex (Allen) key. That is a metric size, so an SAE/inch set will not seat properly and will round the socket out. Keep the 2.5 mm wrench with the fixture for future handle removal.

Screw only. THP4165 is a single setscrew, M5 x 15 mm with a 2.5 mm hex drive. No handle, shank, cartridge, or escutcheon is included, so if the trim itself is damaged you need the corresponding trim part in addition to this fastener.

Match on the TOTO part number stamped in your parts diagram. THP4165 is the M5 x 15 mm, 2.5 mm hex setscrew; TOTO uses several setscrew lengths and drive sizes across its faucet and shower trim, so a screw that is the right diameter but the wrong length will either bottom out or fail to reach the shank flat. Pull the old screw and measure the threaded length before ordering if the diagram is not at hand.

It is a reasonable MRO stock item if your buildings run TOTO trim, since a loose handle is one of the most common service calls and the fix is a 2.5 mm hex screw. Stock the 2.5 mm hex key alongside them. Before buying in quantity, confirm the M5 x 15 mm size matches the screw in your particular trim series, as TOTO uses more than one setscrew across its lines.