The Tecumseh 40004 Piston Assembly STD is a genuine OEM replacement part designed for standard bore Tecumseh engines. This complete piston assembly includes the piston, piston rings, wrist pin, and retaining clips, crucial for maintaining proper engine compression and power output. Manufactured to Tecumseh's specifications, it ensures a precise fit and durable performance in compatible engine models. This assembly is vital for engine rebuilds or repairs, restoring original engine efficiency.