Vixen Dovetail-Plate Mounting Block 3810 Usable with ATLUX Accessory Plate, ATLUX Base Plate or SX Accessory Plate DX and for mounting optical tubes. For installing an optical tube with the standard dovetail attachment. Mounts: Sphinx, GP2, GPD2, Atlux wt. 7.76 oz. Dimensions: 3"Lx6"Wx6"H.