The DVR160 from Losmandy is a pair of 6.3" (160mm) guide scope rings designed to attach a guide scope to your telescope kit.
The rings attach to Losmandy D-series and Vixen "V-series plates via a tool-less dovetail clamp on the bottom of each ring. Once attached, the guide scope may be inserted into the rings and adjusted via three 7075 aluminum positioning screws which feature 1/4" Delrin tips. The I.D. range of these rings is from 5.3 to 6.3".