No need for replacement parts: the plunger pin is set captive for life. These snap shackles are hot drop forged from high strength, high resistant stainless steel. Forging creates a superior steel product, by increasing its elasticity and maximizing the steel's internal strength. A forged snap shackle will deform long before breaking. It will not burst or break suddenly. This is a strong safety consideration. The articulating trunnion head allows the snap shackle to bend in situations where high stress binding would otherwise occur.