So, these gloves have a pocket on the back to put the batteries in. The D size batteries taken by Fisher price toys and boomboxes in the 80's. You have the impracticality of a brick attached to the back of your wrist that gets in the way of EVERYTHING. It's hard and heavy, basically a weapon suitable for smashing reinforced glass. A car battery wouldn't be much worse. After an hour of waiting you'll also realise that the 'heat' generated is no different (if not less) than a pair of cheap woollen gloves. Then you're stuck with a pair of oversized batteries that fit nothing from this century. Great idea if they actually got warm and took a smaller battery.