The new A.R.M.S. (R) #71L series of Front and Rear Sights with STEEL APERTURES! Both are made from durable metal-reinforced polymer and are a good option when seeking a quality sight. The apertures on the rear sight are real steel and not subject to distortion like thin plastic types. Both are .600 when in the folded position from the top of the receiver.Both #71 Front and Rear Sights are designed to allow attachment to all universal dovetail rails. Not for use on Dovetail Gas Blocks.