Absorbed Glass Mat (AGM) Technology is an advanced battery design that eliminates water loss. Once it’s filled with acid, you’ll never need to fill it with water or check the acid level. Long Life Because of its lead calcium design, the AGM battery will hold its specific gravity more than three times longer than conventional lead antimony types. This means much longer periods between charges when the battery is used in a standby mode, like winter storage. And to remain factory-fresh the AGM battery is shipped dry along with its own pack of high- gravity acid that’s added at the time of installation. Non-spillable Once filled with acid from its special packs, the AGM battery is virtually maintenance free. All of the acid is absorbed in the special plates and separators, so there is no need to worry about acid leaks on the valuable vehicle parts and accessories.