This is the Counterweight Shaft Safety Knob that we have sold for years. It has a 5/16-18 thread and fits into all the counterweight shafts we have produced up until the current style 1.875" shafts were introduced in 2006. It is still the standard knob supplied with the Mach2GTO, and is the required knob for all 400, 600, 800 and all older 900 and 1200 mounts.
This knob requires the use of one of the Safety Washers. DO NOT use your mount without the Counterweight Shaft Safety Knob and the appropriate Counterweight Safety Washer!
Recommended for: All Astro-Physics mounts that have been produced.