These let you roll your Celestron telescopes that use the NexStar tripods. Unlike the ScopeRoller product for the Losmandy mounts, these don't slide into the tripod leg. Instead, the tripod leg slides into the ScopeRoller, and three bolts lock the ScopeRoller into position on the tripod leg. The inner tripod legs for the Celestron NexStar are 1.39" diameter.
These are available in Standard, Deluxe, and Deluxe5 versions.