This S7 tool steel Sear fits all 1911s. A3X is a patented Sear can only be used with the A3 Hammer and sold as a set. It does NOT FIRE from the Sear ledge on the Hammer. That location now is a Safety. 3.5 to 3.9 pounds triggers are common with no fitting. See Technical Library for details. Add 3.00 SHI.