NEW PRODUCTION SSK BARRELS, NO FLUTING ON THIS BARREL. PLATFORM: THOMPSON CENTER G1 CONTENDER/G2 CONTENDER/ SSK-50. RATE OF TWIST: 1 IN 7 TWIST RATE. 810 BULL CONTOUR ANY RIFLE FOREND WILL WORK FINE. FOREND SCREW SIZE/SPACING: 10-32/ 3 9/16 CENTERS. THREADS: Yes 5/8-24 THREAD. SCOPE BASE: COMES WITH BLACK OR SILVER 6 HOLE BASE ATTACHED.