These lead bullet casting mould handles will fit most one and two cavity RCBS, Lyman, Saeco and custom bullet moulds. They will not fit four cavity moulds. Bullets are more consistent by the elimination of the variable of mould pressure. The feedback has been overwhelmingly positive from older and handicapped people who have been able to cast with this holder. Feed back has included better bullets (less difference of weight from bullet to bullet), faster, less hand problems and fatique (very common for older casters).