Leupold Standard One-Piece Marlin 336R Black Gloss Base The forward part of the base accepts a dovetail ring, locking it solidly into position Long Range STD mounts provide a 15-MOA slope of built-in elevation compensating for bullet drop at extreme ranges 2-Piece bases offer maximum accessibility to the breech area of your rifle STD rings are engineered to match up with STD 1-Piece and STD 2-Piece bases Forged and machined steel construction