Dlask Arms Corp. 10/22 & DAR 22, scope rails are made out of 6160-T6 Aluminum. They are Mil-Spec Type 3 hard black anodized. You can reverse the rail so it extends over the barrel or have it facing the other way to fit your scope were you want it. You have 3 sizes to pick from ; 3/8" (low), 1/2" (medium), and 3/4" (tall) with a see through bottom. The 3/4" allows you to see through the bottom, allowing you to use your factory sights with it. When reversing the rail, no extra holes have to be drilled in the receiver, as the specific hole pattern in the rail takes care of that and makes it possible that it can be assembled in reverse. Another unique feature of our design regards the optional extra strength and rigidity in holding the rail onto the receiver. For this, your gunsmith will simply drill and tap 2 additional holes #6-48 tpi into your Ruger OEM receiver (this is not required in the case of our DAR-22 receiver, as it already has the extra holes). Package includes 6 mounting screws to fit a standard Ruger brand receiver (but if you intend to use this rail on our DAR-22 receiver, we suggest you take advantage of the receiver's extra thick top and purchase the #6-48 tpi 5/16" screws from our on-line store because they are longer and they provide for a better engagement).