This is an interesting rail for use on many different projects. These have a Picatinny Rail on top and a dovetail underneath. They are about 7 inches overall. There is a lock screw recess on top. Use your imagination and skill to make use of these rails. Great for custom projects. Here's the back story We bought these from a major manufacture that was liquidation inventory. These were originally used to convert A1 and A2 upper receivers into a flat top, back when those were cheep and flat tops were hard to find. So if you have an old upper that has a broken top handle you can repurposed them into a flat top.