The 3.7-volt Thawdaddy battery is compatible with only Mobile Warming Thawdaddy Heated Vests. To learn more about which garments are compatible with what batteries, check out our Mobile Warming® Technology Battery Compatibility Chart . Specifications: Rating: 3.7volts, 2000mAh Input: DC 4.7volt, 750mA Charge Time: 4-5 hours Size Inches: 2.1in x 1.8in x 0.35in Size Metric: 53.3mm x 44.5mm x 9mm Garments Compatible: Smart ThawDaddy Vest