This is a 100mm ID Guidescope Ring that will fit to a Celestron Dovetail Rail.I Printed with these settings; Layer Height: 0.25mm Shells: 2 Infill: 100% (could possible reduce this, but my Scope cost a lot and I didn't want to take any chances) Print each piece (Ring and Ringbase) then use 3mm screws to join them together. Get thumb screws (5mm) 3x per ring from Lowes to hold you guidescope in the middle of the rings. Use an additional thumb screw (5mm) per Ringbase to tighten it on the Dovetail mount.