The Extreme Service thumb safety is the result of years of design and testing to develop a thumb safety that is ergonomically comfortable, rugged in construction and offers unique features that solve many of the problems with existing designs. The thumb shelf has an arced shape that is sculpted to meet the "plate" portion of the safety. The shelf is lowered slightly and rotated on the plate to better match up to the human hand. This makes the safety more comfortable in use over extended firing sessions. The positioning of the thumb shelf also helps keep the palm of your hand in deeper, more solid contact with the grip safety, so it's less likely that you'll have a failur Mfg: Harrison Design & Consulting SPECS: CNC machined from bar stock alloy carbon steel and heat treated to GI specs.