These ingenious storage containers are designed to keep your Art Clay and Precious Metal Clay moist for an extended period of time. Within the lid of each container is a sponge and a perforated tray. The sponge is wetted before securing it into the lid and provides a moist environment, preventing your clay from drying out. Available in two sizes, 1 7/8" dia. x 1" and 2 1/2" dia. x 1 1/2".