DaFin Classic - Black/Red100% Malaysian Rubber All natural, high quality rubber. The blade provides rigid resistance yet is flexible where required. There is less drag on the up kick and leg strain and cramps are reduced. Comfortable Foot Pocket The pocket is silky smooth and soft over the top of the toes and foot to prevent blisters and chafing while the bottom of the pocket is rigid to transmit power to the blade. Fin socks or booties are not required for comfort.