It's designed for treatments on the backside, stomach, arm, thigh, calf and back of the neck. The rounded, narrower edges can also be used to pressurize and knead particularly tense muscles and areas during treatments. 100% Natural Black Basalt; Excellent for holding heat for long periods of time;Rich with iron and magnesium. Shaped and polished by traditional handcraft, no wax, dyestuff, chemicals were applied. Size: 3' x 2.2' x 1.1' , 8 pieces per pack.