The Worlds First Self-Heating Massage Therapy Stones. Sassi-Â (Italian)Â plural. stone, pebble. â€‹This revolutionary new product takes the massage experience to an amazing new level! "Sassi Stones" are self-heating massage stones. â€‹â€‹Made of the highest quality "Moroccan Sand" Stoneware, these therapy stones are battery operated and provide an incredible warming massage for one to two hours per charge! â€‹Warm! Smooth! Feel the heat penetrate your muscles like no other product can!