Selecting a Wichard shackle is a choice for safety. Drop forged for superior strength. The self locking pin is designed for safety. Small indentations in the shackle engage the head of the pin. Final tightening then creates the tension that locks the pin in place. Even the most violent vibrations will not loosen the pin. Stock Dia. 5/16" A 1 1/32" B 5/8" Funct. 2755lb BL 5950lb