This Genuine Tohatsu Marine Part is a piston ring set (O/S) with the part number 346-87124-0. It is designed specifically for Tohatsu outboard motors. The piston ring set is an essential component of the engine's piston assembly, responsible for maintaining proper compression and preventing oil leakage. This particular set is oversized (O/S), indicating that it is slightly larger than the standard size, which can be beneficial for engines that have been rebuilt or modified. The part number 39-16055A 4 may refer to a compatible cross-reference number or a related component. Overall, this Genuine Tohatsu Marine Part ensures reliable performance and durability for your marine engine.