A-B1691792-AI LOCK-PISTON PINOne New Aftermarket Replacement Lock Piston Pin Fits Briggs & Fits Stratton Small Engines This piston pin lock (also called a wrist pin retainer or piston pin retaining clip) secures the piston pin within the piston pin Fits Boss, preventing lateral movement of the wrist pin during engine operation. It is a critical internal engine component used during piston and connecting rod service on Fits Briggs & Fits Stratton small engines found in lawn