Features: Tube rings make from metal,the guide scope rings are suitable for small and mediums sized guiding telescopes,40mm compact finder guidescope set for astrophotography for mounting a guide scope parallel to the main telescope Solid metal guide scope rings for compact finderscope or guidescope with knurled metal screws. big screws with maximums grip allow easy use even with gloves The adjustment crews have inlays for avoiding unaesthetic scratches and pressure marks on the telescope while still ensuring reliables clamping The inner diameter of the tube rings is 40 mm for telescopes between 20 to 40mm tube diameter can be mounted adjustable Wonderful gift,sweet warm gift for friend family and yourself. Specifications: Materials:Alloy Package Includes: 1Set Guiding Scope rings note: Please allow 1-3cm error due to manual measurement. please make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item.