The Hayzee Solid is made of corrugated plastic and can be used as a litter box and/or hay holder for guinea pigs. Corrugated plastic is waterproof and can be easily cleaned. The tall sides prevent hay from falling out of the cage and scattering throughout the cage. Sizes: Large- 26.25"L x 13.25"W x 10.25"H - The front lip for entry is 3" tall. This size is made to sit between 2 grids at the end of a cage for C&C cages which use 13.8"/14" grids or to stand alone in a large cage. Medium- 23"L x 11.5"W x 8.25"H - This size is made to sit between 2 grids at the end of the a cage for C&C Cages using 11.8"/12" grids or to stand alone in a cage. Our 1x2 Liners can be used with the Hayzee Solid 26.25"L x 13.25"W x 10.25"H as an absorbent bottom. Other useable material to place under hay for absorbency is bedding pellets, paper bedding, or shavings.