Absorbed Glass Mat (AGM) Technology is an advanced battery design used in Yuasa's Maintenance Free Batteries that eliminates water loss. Once it's filled with acid the battery is permanently sealed - so 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. Sealed, Non-spillable Once filled with acid from its special packs, the AGM battery is virtually maintenance free. It's totally sealed and all of the acid is absorbed in the special plates and separators, so there is no need to worry about acid leaks on valuable vehicle parts and accessories. Comes with pre-measured acid tubes that need to be added prior to installation. Includes a seal that is then placed across the top of the battery to create a sealed, spill-proof battery. Never needs refilling, but may need periodic charging. Includes 1-year manufacturer's warranty.