These sturdy, inexpensive terraria are perfect habitats to consider if you don't have a jar or container of the right shape and size. Both are square in shape, with the 1-gallon size taller than the 1/2-gallon. They are made of sturdy, semi-flexible molded plastic that will not easily crack or break. The lids fit snugly, but not tightly, and have built-in airholes. The 1/2-gallon size is great for small creatures or fish, while the 1-gallon size is recommended for plants and somewhat larger creatures. - Jess