Check the listing for details. William Optics Red Cat51 Mount for ZWO EAF Focuser. Condition: New. Listed at 55.00 USD. This mount is designed for use with the ZWO EAF Focuser with ASI AIR PRO/PLUS or a mini PC like the Mele Quieter 3/4 series on the William Optics RedCat 51 telescope. It comes with a variety of mounting options to attach the ZWO ASIAIR mount, finder shoe, RedCat original finder handle, MINI PC mount, and so on. The mount is made from durable PETG or ASA material of your choice. I have used a similar belt design for years in all my setups with helical focuser telescopes, starting from the ASKAR FRA 130, ASKAR FRA 180, Rokinon 135 F/2, and now RedCat, and I have had no issues with it. Once set up, check the belt tension from time to time. Gear ring is designed to fit GT2 belt so it does not require a lot of tension, just enough to rotate the telescope's focuser as well as the RedCat focuser tension.What Option to Choose: They all work similarly well. The difference between ASA and PETG versions lies in temperature resistance: ASA can withstand up to ~90°C (194F) before bending/melting, while PETG can handle up to ~70°C (158 F). So if you are going to do astrophotography in hot Texas weather, I would probably go for the ASA version. The difference in the gear ring split/single just matters whether you need to take off RedCat's dew shield or not while installing the ring. Sale does not include: RedCat51, Mini PC, ASIAIR, Focuser shown on the pictures. Sale Includes:3D printed Focuser / Accessory MountGT2 belt3D Printed GT2 gear ringAluminum GT2 pulleyScrews Please let me know if any questions.