Made of good quality metal in yellow, features high elasticity and good precision, installed small size and generate strong force.This Mould Die Spring is widely used in the punching moulds, metal die-casting moulds, plastic injection moulds and mechanical equipment with rigid structure.Hole Dia:The Diameter of the Hole on the Mold ,i.e.the Outer Diameter of the spring Rod Dia: The Diameter of the Rod that is to be inserted into this spring, i.e.the inner Diameter of the spring