The 125mm Guidescope Rings from Celestron are made to accommodate up to a 102 millimeter guidescope (finderscope). Made to slide onto a dovetail bar, alignment pins have been designed in the rings to keep both ends of the clamp parallel. There is a spring loaded clamp to prevent the binding of the ring clamps on the dovetail bar when the tightening knob is loosened. It has a large CGE Style clamp for more secure attachment and is compatible with Losmandy bars. The large and ergonomic knobs allow for an easy and secure attachment.