This Rail Adapter replaces the sling swivel stud on the for-end of your rifle to enable the quick detach of the Evolution Bi-Pod. This Rail Adapter includes a sling swivel attaching point, as well as an anti rotation flush cup receptacle. Includes Screws and hardware for installation. $29.99
 
Hole spacing is .75" between each hole.  The two holes farthest apart are 1.5" apart.  
Usable Picatinny rail is 2" long. Total overall length is 3"