The Shield Action Enhancement Trigger Kit directly replaces the factory hinged trigger with a solid aluminum trigger body. The trigger reduces Trigger pre-travel and over-travel by approximately 20%. It features a flat face with a center mounted pivoting safety. The center mounted pivoting safety bar prevents unintended operation by creating a trigger block that will not disengage unless the shooter places their finger directly on the trigger face. The flat, smooth face trigger causes the shooter to place their finger on the center line of the trigger and encourages trigger manipulation directly in line with the bore axis. The Shield Action Enhancement Trigger is perfect for use with the M&P Shield already equipped with the Apex Shield Carry Kit. This kit is a combination of the Shield Duty/Carry Action Enhancement Kit and the Shield Action Enhancement Trigger. The APEX Shield Carry Kit Kit (SCK) was designed to provide the M&P Shield pistol owner a smooth, consistent 5 - 5.5 lb trigger pull 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. The kit itself is engineered to be drop-in and should not require further gunsmithing. However, armorer or gunsmith installation of the USB into the Shield slide is strongly recommended**. Fits Smith & Wesson Shield in 9mm and .40 S&W. Parts Included: Fully machined Sear Ultimate Striker Block Kit Ultimate Striker Block Striker Block Spring Talon Tactical tool Shield Carry Spring Set Sear Spring (1/8") Slave Pin (to assist with trigger return spring installation) 4 lb Rated Trigger Return Spring