I use racks designed by PM herps. The tubs are really small and fit very tightly into the rack. I put newborn NA milks in these with no problems.the tubs are maybe 3 inch by 6 inch by 1.5 inch high.

Here is a pic of the rack in one of my snake rooms on the left side of the picture.

Also, google PM herps and check out the website for more info.

Dave
DNS Reptiles - Milk Snakes