Strike Picatinny Stock Adapter, Si Ar psa bk Ar Picatinny Stk Adaptr Personal Protection The crossbill's hollow ground blade is The crossbill's hollow ground blade is manufactured using 8cr13mov stainless steel and a front D ring can attach to a crotch strap The strike ar picatinny stock adapter mechanism threads into a standard ar rear 1 3 16" 16 hss right hand thread and has an anti loosening detent that is very positive and tactile while keeping the rear detent spring captured for the rear takedown pin quickly convert your ar lower receiver to mount a picatinny stock or stabilizer with the strike ar picatinny stock adapter