Orion 7377 298mm ID Telescope Tube Rings Set of two cast-aluminum telescope tube rings with quick-release, hinged clamp knobs and felt lining Use these tube rings to attach an Orion 254mm f/4.7 reflector telescope optical tube assembly to a mount or dovetail mounting plate One tube ring has 1/4"-20 piggyback camera adapter; the other has threaded 1/4"-20 hole For use with 10" (254mm) f/4.7 reflector optical tube assembly. Not compatible with Orion 10" f/3.9 Newtonian Astrograph Reflector. See compatibility table below. Mounting bolts and washers are included