This is a Timney Triggers Trigger known as the AR Calvin Elite, model 660CE.
Timney set the standard for aftermarket trigger upgrades for the AR/M4 rifle. This trigger features Ultra-reliable 5-pound hammer spring coupled with a crisp and zero creep 1.5-pound pull weight. Trigger shoes are adjustable for length of pull" cast and height for the ultimate in custom comfort and positive contact.
Adjustable for Custom Feel