Tire ring sizes

He is wanting to know what the inside diameter of the rings are to make his own..I believe is how I read his question...not to buy jones rings....
I believe the most common size rings are, 34", 33", and 32 1/2", to adjust your tires larger or smaller than the rings, stretch or shrink them to get the stagger you desire.
WHat is the advantage of these over adjustable rings?

Consistency.... You can keep your tires close to the same size everytime.
Also the tires stay round and have no dips or anything where the adjustable band will a lot of times leave a hump where the two pieces of the band overlap.