NEW PRODUCTION SSK BARRELS. PLATFORM: THOMPSON CENTER Encore PROHUNTER. RATE OF TWIST: 1 IN 7 TWIST RATE. 810 HEAVY CONTOUR ANY RIFLE FOREND WILL WORK FINE. FOREND SCREW SIZE/SPACING: 8-40 / 5 Centers. THREADS: Yes 1/2-28 THREAD. SCOPE BASE: COMES WITH BLACK OR SILVER 6 HOLE BASE ATTACHED.