The Apex Tactical S&W SD 9/40 Spring Kit is a drop in spring kit provides a smoother trigger pull and improved reset along with lowering the trigger pull weight for 8 to approximately 5.5 lbs. This high-quality Apex Tactical spring kit for Smith & Wesson model SD pistols works as a stand-alone or in conjunction with the Apex SD Polymer Action Enhancement Trigger. This model 107-120 Apex Tactical spring kit inlcudes Apex Trigger Return Spring, APex Striker Block Spring, Apex Striker Spring, and Apex SD Slave Pin to assist in installation of Trigger Return Spring.