... chains 1. material: alloy steel 2. color : blue, black, yellow and natural B series roller chainsSpecification:1. Simplex: 04B-1, 05B-1 ... ,72B-1.2. Duplex: 05B-2, 06B-2, 08B-2, 10B-2, 12B-2, 16B-2, 20B-2, 24B-2, 28B-2, 32B-2, 40B-2, 48B-2, 56B-2, 64B-2, 72B-2.3. Triplex ... standards.Color: blue, black, yellow and natural industrial transmission chain (B series)