This is a Apex Tactical Specialties Trigger known as the S&W SD, model SDSPRINGKIT.
The Apex SD Spring Kit produces a smoother trigger pull and improved reset and is designed for Duty/Carry use. The kit works as a stand-alone or in conjunction with the Apex SD Polymer Action Enhancement Trigger.
Features:
Reduces trigger pull weight by approximately 2.0 lbs. from factory
Smooths trigger pull
Improves reset
