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