“DSR” Hubs – for assembly with “AR” plate sprockets to make double-single of substance sprockets. Finish bore hubs have got standard keyway and 2 setscrews.
Ready Sprockets are a READY SPROCKET HUB TYPE DSR 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 completed bore hubs to support shaft sizes through 2-3/4″ diameter, 
and also a variety of square, hex, spline, and tapered essential bores.