The Lee Black Powder Minie Mould - Single Cavity is the perfect choice for reloading. The aluminum material provides rust resistance and the moulds are capable of heating up and cooling down more quickly than moulds made from steel or iron. This mould is also much lighter weighing roughly 33 percent less than steel and iron moulds.Another benefit is less fatigue during reloading sessions. This mould is CNC machined for perfect roundness and control of size. Keep in mind that while the mould is sold according to weight for suggested alloy there could be slight variances.