Bases are 5 inches in length. 3.2 inches from the center of the rear ring slot to the center of the inner front ring slot. 4.0 inches from the center of the rear ring slot to the center of the outer front slot. .275 inches height measured from the top of the barrel radius to the top of the base. Bases are cut to standard Weaver dimensions. Bases are packaged with the appropriate number of 6-48 x 1/4 Torx head attaching screws and a T-15 Torx head key. Bases are radiused to fit either the 1.00 inch Encore barrel diameter or the .810 inch Contender barrel diameter.