ARRIS Heating pad for Knee Package for this heated warm knee support only includes 1 pcs, so we suggest you buy 2pcs at a time to use on both knees. Perfectly suitable for Father`s Day Gift, thanksgiving gift and christmas gift. 7.4V Powerful Rechargeable Lipo Battery Offers Unmatched Power - Almost all heating knee wraps in the market are powered by 5V batteries, while we use 7.4V battery, which offers unmatched power to the heating knee pad.