Self-adjusting tensioner, Arm Rotation 70 Degrees , For Chain Number Not Applicable, For V-Belt Size B, Pulley Outside Diameter 4 in, Maximum Tension Force 42 lbf, Arm Length to Hole Center 4.5 in, Arm Material Aluminum, Features Automatically Take Up the Slack and Avoid the Risk of Over-Tensioning Drive Components to Enhance Overall Drive Operating Efficiency, Housing Material Aluminum, Includes RT3000 Tensioner, VX0285 Pulley, Minimum Tension Force 0 lbf, Mount Hole Diameter 33/64 in