The Vmaxtanks XTR31-135 is an Extreme Series 12V 135AH Deep Cycle AGM Battery. Sealed Construction The unique construction and sealing techniques of VMAX tanks guarantee leak proof operation in any position with no adverse effect to capacity or service life. VMAX tanks are classified as non-Spillable, non-hazardous, dry batteries making them NOT restricted for Surface, Maritime and Air Transport. Electrolyte Suspension system VMAX tanks utilize an electrolyte suspension system consisting of AGM (Absorbed Glass Matt), a high porosity that totally absorbs and contains the electrolyte. No silica gels or any other contaminants are used. Maintenance Free Operation