The Malcolm 3X and 6X short scope rear mounts are designed to fit onto the 1/2" wide 60 degree base. The standard mounting set for the Malcolm 3X and 6X short scopes comes with two predrilled 1/2" 60 degree bases. The hole spacing for the predrilled bases is 1/2" from center to center.
Once this piece is drilled and tapped into your receiver and barrel, you can slide the front and rear mount onto these bases to finish mounting your Malcolm 3X or 6X short scope.
We also offer a blank 1/2" 60 degree base for rifles whose drilled and tapped hole pattern does not match that of the provided predrilled bases.