Just place the heat pad in the microwave for approximately 2 minutes and the gel bag inside the cushion will heat up and store the warmth for up to 4 hours. It is totally safe and lasts up to 4 years. Snuggle down in bed with the heated cushion and enjoy hours of cosy warmth. It will relax your muscles and you will fall asleep quickly and easily. And the healthy sleeping temperature will ensure that you are thoroughly rested. Measures 29 x 19 x 2cm (11 1/2" x 7 1/2" x 3/4"). Cover 100% cotton, filling 100% polyester. The cover is machine washable at 40°C in the delicate cycle.