A-B1825036-AI RING SET-STDOne New Aftermarket Replacement Standard Piston Ring Set Fits Briggs & Fits Stratton Engines This standard (STD) piston ring set is a direct aftermarket replacement Fits Briggs and Stratton gas engines. The rings seat in the piston grooves to create a combustion seal, maintain cylinder compression, and prevent oil from entering the combustion chamber. This is a standard bore set intended for use with standard (non oversize) pistons and cylinders.