Factory-Activated AGM Maintenance-Free: Heavy-duty batteries ideal for recreation and ATV racing. Maintenance-free. Pre-filled, sealed, charged and ready to go. Spill-proof design. Sulfation retardant. Advanced lead-calcium technology. Remarkable resistance to vibration. Vast impact in extreme weather conditions. Note: Factory-Activated batteries should be charged once a month when not in service. (Standard) AGM Maintenance-Free: Heavy-duty maintenance-free 12-volt batteries offering the quality you expect from MUD at affordable prices. Superior vibration resistance and durability provide a long service life. Holds a charge three times longer than conventional batteries. Absorbed Glass Mat battery eliminates water loss, permitting the battery to be permanently sealed once it is filled with acid.