1.5 Inches thick rubber foam . Covered with brown suede micro fiber on one side and synthetic lamb"s wool on the other side . Removable cover with a zipper . Machine washable cover . Provides exceptional comfort and insulation from the wood floor . Small: 29.5 in. L x 18 in. W . Medium: 37 in. L x 21 in. W . Large: 41.4 in. L x 24.6 in. W