I purchased this along with the dual motor focus controller. The install instructions were inadequate. The unit also shipped without the screws to attach the unit to to bracket. I bought screws at home depot (#3 metric). The instructions indicated the bracket should be installed over the orange celestron retaining ring and to use the provided longer screws. On my scope (14" EdgeHD) the provided screws were the same length as those removed from the scope. I had to remove the orange retaining ring entirely to allow all the parts to line up. Tensioning the belt is quite difficult as the tensioning screws are hidden behind the unit (in the space between the unit and rear of telescope) so a great deal of dexterity is required to tension the belt and simultaneously tighten the screws using an allen wrench. For my installation I required three different allen wrenches - none of which were provided. The unit turns much slower than expected but it does focus the scope appropriately. The unit appears to be solidly built with good fit and finish. I got this unit as a replacement for a celestron focus motor which had immediately failed on my telescope.