La description

The coupling is used to transfer some power by connecting the drive shaft with the driven shaft.

The coupling is providing a wide range of choices in how to tighten the shaft.
It consists of corrosion-resistant aluminum alloy (Duralumin) with light and high stiffness,
so a revolution system with a small inertia can be driven.
It includes DRB, DRBS, DOH, DOHS, DJC, DJCS, DRJT, DRG, DRGL and etc.
other than DRN, DRJ and DRP.

There are 3 types in how to tighten the shaft.
There are one set screw type and 2 clamp types in how to tighten the shaft. One of them can be optional.
Based on which type can be optimized, 
different types or the diameter can be chosen depending on the shaft where the and output are located.