These remove all the slop between the trigger, hammer, pins, and the receiver and results in that extra bit of refinement to get the maximum performance potential out of high grade parts. These tool steel trigger/hammer pins are available in .156 for small pin receivers and feature custom buttomhead stainless retainer screws (matte black finish) on both ends for corrosion resistance. o modification to the lower receiver is needed, but be aware that the trigger and hammer may have to be reamed for a perfect fit with these parts. The downside: installation is a bit more difficult over stock pins and detail stripping the lower receiver will require a bit more care. Finish is black oxide.