This is the new style 18/20″ Moving Vise Jaw, it is made from fabricated steel and this vise is extremely durable. It features an offset clamping which helps to balance the clamping force with the rock being held on the left side of the vise. This vise is not compatible to be used with the cast iron Fixed vise jaws and should only be used with 20046 (Fixed vise Jaw) and 200039 (Vise Lock)