Mine are in 41-quart tubs in a rack. The smaller (under 1000 gram) BP's have two hides, one on the heat and one on the cool side. Above that I notice they really don't use the cool side hide much, so I just give them one on the warm side and occasionally I find they've shifted it off the heat themselves. My largest girl is almost 1900 grams and she has no hides, the tub is her hide.