In the pockets, it works well because it heats up a lot. There is a huge difference if you hold it with the case or without it. When it comes out into the atmospheric air (with or without the case), it immediately loses its warmth. Also, it doesn't last 12 hours, but a maximum of 6 (always with a full charge. The accompanying container has an indication for 12 hours, so you know how much liquid you put in.)