This Genuine Tohatsu Marine Part is a Piston Ring Set (0.5O/S) with the part number 3C8-87124-0. It is designed specifically for Tohatsu outboard motors. The piston ring set is an essential component of the engine's piston assembly, providing a tight seal between the piston and cylinder wall to ensure optimal compression and combustion. This particular set has an oversize measurement of 0.5O/S, indicating that it is slightly larger than the standard size to accommodate for wear or damage to the cylinder wall. It is recommended for use in specific Tohatsu outboard motor models. Additionally, the part number 39-16055A 5 may be an alternate or cross-reference number for this piston ring set.