The 3.35" and 4" 1913 Picatinny Rail  will accommodate hole patterns with a center to center spacing of 1.76 –  2.78" / 2.2 – 3.5" and a FLAT back to accommodate curved surfaces. It also has  a flush cup allowing the use of Flush Cup sling swivels and sling studs (neither provided).
A  standard sling stud and sling stud spacer can be used as one fastener  or two button head machine screws can be used. NO HARDWARE INCLUDED.  See BT1517 to attach this rail to the forearm of standard rifle stocks.
Machined to Picatinny rail standards from 6061-T6 aluminum with Mil-Spec Type III Class 2 finish. Available in black only.
Weight: 0.92 / 1.20 ounces