Mount Ring Set for 4” Diameter Tube provides a rigid means of holding any 4" diameter telescope tube. The individual rings can be spaced any distance apart or from 5.5" to 6.5" apart with the accessory bar or bottom plate attached. This flexibility allows the Mount Ring Set to accommodate a variety of mounts. Each ring has two accessory channels with #10-32 tapped holes, and a #¼"-20 tapped hole on the top and bottom to accept the accessory bar, bottom plate, a stud or bolt as necessary. The accessory bar has a variety of holes to accept Tele Vue Starbeam and even a slot with which you can piggyback a smaller Tele Vue refractor. The included bottom plate (BPL-1098) is drilled to mate to a variety of mounts or mounting adapter plates - including the Tele Vue/Vixen Mount Adapter (AVT-1011) and Tele Vue Gibraltar-5 Head.