Mercury Systems Support GSFA. "Replaces top holder on Guan Shang/Synta made Dob and focuser including those from Orion (Skyquest & Intelliscope), Hands On Optics, Hardin, Anatares, Skywatcher, OPT and others. Gives 2" Brass Compression Ring."
I have an original Orion XT8 Dob (GS), which originally came with a 1.25" focuser only. I upgraded the focuser to a Japanese 2" model. When MSS produced these 2" compression ring screw in replacements I ordered one hoping it may fit my non-standard 2" focuser which it doesn't. It is brand spanking new because it is the wrong size. Also included are the optional Brass Screw Knobs. More info can be had at the web site (Mercury Systems Support - GSFA Adapter).
$20.00 shipped Priority Mail, Postal Money Order only, CONUS only.