R” Hubs – For Assembly With “AR” Plate Sprockets
Circular bore hubs have standard keyway and 2 setscrews. Square, Hex and Splined bore hubs possess set screws only.
Ready READY SPROCKET HUB – TYPE R Sprockets are a variety of sprockets and hubs drilled and tapped for simple, convenient assembly with standard hex head cap screws. For No. 35 through No. 100 Chain, with stock completed bore hubs to accommodate shaft sizes through 2-3/4″ diameter, and also a variety of sq ., hex, spline, and tapered 
important bores.