28B B Series Roller Chain 1.material:40MN/A3 2.pitch:44. ... :7.5/6.0mm 4.surface treatment:heat treatment 28B B Series Roller Chain1.material:40MN/A32.Standard Chain3.color:black ... chains: 428SO,520SO,525SO,530SO3. Roller chains: A series and B series4. Silent chains: SC3,SC4,SC5,SC6,SC8,SC105. PIV ...