This is a CMC Triggers Trigger known as the 2-Stage Flat, model 91504.
CMC's innovative" self-contained and easy-to-install AR-15 trigger groups have been completely re-tooled to maximize production capacities" incorporate new design enhancements and reduce cost. CMC's AR-15 trigger groups have always yielded exceptional trigger pull dynamics for thousands of satisfied customers.
Features:
AR-15/AR-10
Drop-in
Positive Trigger Reset
Easy to install