THESE BARRELS ARE MADE BY SSK IN PA USING GREEN MOUNTAIN BLANKS. PLATFORM: THOMPSON CENTER G1 CONTENDER/SSK50/G2CONTENDER. RATE OF TWIST: 1-7. 810 BULL CONTOUR ANY RIFLE FOREND WILL WORK FINE. FOREND SCREW SIZE/SPACING: 10-32, 3 9/16 Centers. THREADS: Yes 5/8-24 w/Cap. SCOPE BASE: 6 HOLE BASE PICATINNY STYLE FACTORY INSTALLED.