I don't use hides in my racks anymore, but in my PVC's I had some of the exo-terra hides.

Used the Larges for 600-700 or until they started to left the edges when they were inside.
XL's were the next step, had a 1800g is one with no problems.

RB PVC hides are nice too, all depends if you want more of a natural display look in your tank, tuib, rack or whatever you are using.