Timney Skeletized AR15/AR10 TriggersSkeletized Replacement of AR-15 and AR-10 Fire Control Group Timney Triggers for AR15 and AR10 are also called the Fire Control Group. This unit replaces creepy two-stage triggers with a single stage that is smooth and crisp. These triggers are available pre-set for 3 lbs or 4 lbs pull weight (4 lbs AR10). Installation Instructions are easy to follow as this is a true 100% drop-in trigger with no adjustments required. The installation uses your original hammer/trigger pins and the system eliminates pin rotation and walkout. They fit ARs with "small Pin" (.152-157") Hammer/Trigger mechanisms.