Whiddens' hand-polished sizer dies have a shorter overall length for better shoulder bump back, a smaller base and tighter internal tolerances. All of their sizer dies include a shoulder datum collar to measure shoulder bump and headspace. The sizing dies also include a pin retainer should you chose to use the sizer without the expander. Wide knurling on the die make small adjustments simple while the 6-32 machine screw on the lock ring secures the die once the final adjustment is made. Mfg: Whidden Gunworks