BT78: SIG SAUERA(R) CROSS(TM) Buttstock Rail Kit is a 2.05a ^2 1913 Picatinny Rail that installs directly onto the folding buttstock of the SIG SAUERA(R) CROSS(TM) rifle to allow for mounting our Accu-Shot Precision Rail Monopods (BT12-QK, BT13-QK and BT31-QK). Installation requires two factory 10-24 threaded holes spaced approximately 1.57a ^2 apart as found on our sample SIG SAUERA(R) CROSS(TM). No modification is required. Comes with two 10-24 x 3/4a ^2 flat socket cap screws as seen. Use of a thread locker upon installation is suggested. Machined to Picatinny rail standards from 6061-T6 aluminum with Mil-Spec Type III Class 2 finish. Available in black only.