A specialized form of breathing apparatus is called an artificial gill suit (AGS) or simply a “gillsuit”. Unlike a tank-style breathing apparatus that holds compressed air, or a backpack-worn "gillpack" that extracts oxygen from water , an AGS covers the wearer’s entire body. It is made of a material similar to that used in skeinsuits, and may be left transparent or colored as the manufacturer desires. Normal goggles may be worn with an AGS by human, vrusk, and yazirian divers. Due to the thermal properties of water, such goggles may not have infra-red capabilities.