I have an APEX spring kit installed on my S&W SD40 and the trigger is smooth and ideal to shoot. It has a really bad trigger before I installed the Apex kit. I had the spring kit installed by a gun smith and did not try to do it myself. It cost $100 to get the gun smith to do it, so with the cost of the kit, I guess I may have well bought a Walther that comes with a 5.5 pound trigger. Or a Bersa that comes with a 3.9 lb trigger. But the SD S&W gun is now great to shoot.