R” Hubs – For Assembly With “AR” Plate Sprockets
Round bore hubs have regular keyway and 2 setscrews. Square, Hex and Splined bore hubs have got set READY SPROCKET HUB – TYPE R 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 share completed bore hubs to support shaft sizes through 
2-3/4″ diameter, plus a variety of square, hex, spline, and tapered important bores.