All Kritter Keepers have well-ventilated lids in assorted colors and may be used as space-saving aquariums or insect havens, but are also ideal for use as small animal carriers, kritter totes, terrariums or nurseries. Rectangular Kritter Keepers® have self-locking lids with hinged viewer / feeder windows, an airline access hole and an attachment hole (except Mini and Small sizes). The Mini, Small and Medium sizes have carrying handles for easy transport.