21RX/21RG Exhaust Adaptor No.4 O-ring Seal - OS22826133 by O.S. Engine  [OS22826133]

Exhaust adaptor seal for 21RX and 21RG engines

This O-ring is a small-scale RC replacement seal made specifically for Exhaust Adaptor No.4 used with the 21RX and 21RG units. It sits between the adaptor and the exhaust manifold to prevent leaks that can upset exhaust flow and repeatability on model engines.

Compatibility is restricted to the adaptor designation shown in the product title, so verify your adaptor is No.4 and that the engine model is a 21RX or 21RG before fitting. The part is supplied as a single O-ring intended as a routine service item rather than a performance upgrade.

Installation notes: check mating faces for old gasket residue, dirt, or burrs, place the O-ring evenly into the adaptor groove, and avoid twisting or pinching the ring when assembling. Replace the O-ring if it shows compression set, cuts, or glazing. A correct seal helps preserve consistent exhaust conditions for tuning and track use.