Size: 42.0 x 42.0 cm After undergoing 300 million years of geological processes, Yakuo Stone possesses a unique and powerful magnetism. Its distinctive health benefits, which regulate various bodily functions, have gradually been discovered, leading to its designation as "Yakuo Stone." Customers who have used it have reported relief from headaches and stiff shoulders. I think it's good to put about 2-3 sheets on the bed. By the way, I put 3 sheets between the futon and the sheets. It's very popular and sold out quickly last time. We offer a discount of 200 yen per item from the second item purchased. 2 items purchased: 200 yen discount 3 items purchased: 400 yen discount 4 items purchased: 600 yen discount Thank you very much!