DNZ’s Game Reaper is precision machined from a solid block of top-grade billet aluminum and is custom made to fit each type of firearm and align perfectly with your rifle receiver with no moving parts between the firearm and the scope. This Game Reaper model fits all 2010 and newer break open black powder barrels and all years of center fire rifle barrels. The Game Reaper absorbs shock and withstands temperature extremes better than steel mounts. Base screws are 8-40 X 1/4 long. Ring screws are 6-40 X 5/8 long. Base screws use a 9/64 Allen wrench and ring screws use a 7/64 Allen wrench.