This sight is truly Hunter Defined, engineered to what the hunter asked for: precision pinpoint accuracy coupled with lightweight maneuverability. With the NEW Pro Hunter HD, you get all the industry-leading features of the Ascent Verdict, but with the Pro Pin. The addition of the Pro Pin provides a narrower pin throat that ends in a round pinhead. This smaller throat allows for less target obstruction, as well as a more defined aiming point. Now you can finally see what youre aiming at. Micro-adjust 1st and 3rd axes. 2nd axis adjustability. 2X or 4X lens adaptable (optional) makes target easier to see. The indicator needle is indexable for easy re-sighting should your setup change. Available in Pro X Base (pictured) or the 4 Wing Truss. Housing Diameter: 1 3/4 (INSIDE DIAMETER).