The apex duty/carry kit for the m&p shield was designed to provide the shield pistol owner a smooth, consistent trigger pull that is approximately 2 lbs lighter (based on variations in factory tolerances) with the advantages of shorter over-travel and more detectable trigger reset.All of the components work together to provide a pull weight within the acceptable range for a top-end, service pistol.However, armorer or gunsmith installation of the ultimate striker block (usb) into the shield slide is strongly recommended.This kit includes 2-dot fully machined sear, ultimate striker block, striker block spring, talon tactical tool, sear spring, slave pin and trigger return spring.Model: Enhancement KitMaterial: Metal