Orion 7369 76mm ID Telescope Tube Rings Set of two cast-aluminum telescope tube rings with quick-release, hinged clamp knobs and felt lining Tube rings allow you to securely attach a telescope optical tube to a mount and tripod Sold in sets of two rings with mounting bolts and washers are included One telescope tube ring has 1/4"-20 piggyback camera adapter; the other has a threaded 1/4"-20 socket Inside tube ring diameter is 76mm