The Hot Stone Introductory Set now includes two medium-sized S-rank stones. This set can be used in a wide variety of applications. S-rank type stones: 4.7cm x 6.7cm - 4 pieces S-rank stones: 6.5cm x 6.5cm - 2 pieces Small stones: 3cm x 4cm - 8 pieces Total: 14 pieces Improves blood circulation, relieves muscle tension, promotes relaxation, and aids detoxification. Supports the autonomic nervous system and provides total care for the mind and body. Important! Hot stones are not just warmed stones. They penetrate deep within the body. High density is key! The stones (basalt) are made from volcanic lava. They excel at retaining heat and are known for their far-infrared effects, healing properties, and natural geothermal energy effects, among many others. Because of this, they have been treasured as mystical stones by Native Americans and have been passed down to the present day.