Firsttime building a rack myself but I was sick of the HUGE concrete mixing tubs Ihad in the other rack that I had bought.
Went with a much smaller tub from Freedom Breeders. 9.25 x 21.5 x 3.5 W x L xH. I bought one tub to make sure the adults would fit and they do! So, I bought15 more to have a 4 x 4 sized rack.
The tubs were $7.50ea...
Pricey but I got the exact size I wanted AAAND they're specifically made for rodents! Durable with no edges on the inside for chewing.
Just got done with the first shelf! Will update once it's complete!