I use Reptile Basic jumbo hides for my 8 ft retic, 6 ft boa and 7 ft boa and they got plenty of room. http://www.reptilebasics.com/jumbo-hide-box
Can also go to a restaurant supply store and buy a bus tub or Home Depot and get a cement mixing tub.
Here is a pic to give you an idea. This is Caesar my 8 ft retic and you can see he has plenty of room in there. He only uses about half the hide.
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