Maintenance Free batteries. No need to add water, but periodic charging required when not in use. Battery has Absorbed Glass Mat (AGM) Separators – an advanced battery technology that eliminates the need to ever add water. Advanced lead-calcium technology – holds its specific gravity more than 3 times longer than conventional lead antimony batteries.

Advantages:

No need to add water
Higher cranking power
High capacity

Disadvantages:

Activation needed
Impossible to send by package