Harrison Design Extreme Service Beavertail Grip Safeties are CNC machined from bar stock, either stainless or carbon steel or 7075 aluminum and are engineered to allow the craftsman to create that "hairline" joint beavertail installation that everyone wants. Dimensions are left oversize in the critical places, such as in the width of the center lug of the beavertail that fits between the frame tangs, eliminating the need to weld in between the frame tangs in the majority of cases. The side to side dimension of the 'tail is also left oversize to allow fitting flush with the flats of the frame. The fitting radii are machined undersize at a .240" radius to allow enough material for proper fitting of the beavertail to frames that have already been machined for a .250" beavertail by the factory and left a bit looser than desired. The blocking arm comes with the "Take Down" notch already cut for you.
Please be aware that beavertails are definitely not drop-in parts and require fitting by a skilled craftsman to result in a fit to be proud of. If your skill set and tooling are not up to the challenge, please seek professional assistance.
When fitting a new beavertail, remember that the joint is a three-element fit between frame, grip safety and your thumb safety. Because the shaft diameter varies between all the different thumb safeties on the market, it's a smart move to replace the thumb safety at the same time you fit the grip safety, if you have any intention of replacing it. You could go through all of the work to fit a beavertail and then decide to swap safeties afterwards and find your nice tight hairline joint has loosened up when you slip in the new safety.