Flat Herringbone Chains HB-35 (1.6 mm – 1.7 Gr./Ft.) HB-40 (1.8 mm – 2.5 Gr./Ft.) HB-50 (2.4 mm – 3.6 Gr./Ft.) BHB-60 (2.7 mm – 6.0 Gr./Ft.) BHB-70 (3.2 mm – 6.7 Gr./Ft.)