Review on 24-Pack SunnyBay Pain Relief Patches: Air-Activated Heat Therapy Pads For Lower Back Pain, Neck, Shoulder, Menstrual Cramps And More, 4 Reusable Belts, Up To 113°F Temperature by Christy Ghosh

This includes four reusable velcro belts where you can insert the heat patches to use around your body and have it stay in place. The heat pads themselves are air activated and take about 20 minutes to heat up after opening. This is advertised for pain relief but I found these to be on the milder side in terms of heat. These are much better for use to relieve menstrual cramps more so than knee and muscle pain. They are very easy to use though and the wearable belts are a well thought out addition.