Short Pitch Precision Roller Chain (A Series) A Series: 25, 35, 41, 40, 50, ... , 100, 120, 140, 160 All with simplex/doubl Model:Short Pitch Precision Roller Chain (A Series): 25, 35, 41, 40, 50, 60 ... with fine Steel, Automatic Heat Treatment Equipment and Automatic Assembling. Short Pitch Precision Roller Chain (A Series)