Celestron 125mm Guidescope Rings 125mm rings are large enough to accommodate up to a 102mm guidescope Alignment pins keeps both ends of clamp parallel when sliding on to dovetail bar Spring loaded clamp prevents binding of ring clamp on dovetail when tightening knob is loosened Larger CGE Style clamp for more secure attachment and compatibility with Losmandy bars Large and ergonomic knobs for easy and secure attachment, even in the dark