These Digital Color Balance Cards are spectrally neutral under all lighting conditions giving a true and accurate representation of the physical qualities of the light illuminating the card. They are made of a unique material that is resistant to moisture so they won't warp. This enables them to be washed with mild soap and water if they become soiled. The color permeates the material making the cards 2-sided. If the cards become scratched, they may be lightly polished to restore the surface. They measure 8x10", are flexible and more durable than standard cardboard gray cards. Available in a reusable clamshell package of 3 cards: one each of white, gray, and black.