NEW PRODUCTION SSK BARRELS. PLATFORM: THOMPSON CENTER G1 CONTENDER/G2 CONTENDER/ SSK-50. RATE OF TWIST: 1 IN 14 TWIST RATE. 810 BULL CONTOUR ANY PISTOL FOREND WILL WORK FINE. FOREND SCREW SIZE/SPACING: 10-32/ 3 9/16 CENTERS. THREADS: Yes 11/16-24 THREAD. SCOPE BASE: COMES WITH BLACK OR SILVER 6 HOLE BASE ATTACHED.