Lovyou 7pcs Hot Spa Rock Basalt Stone Massage Stones Massage Lava Natural Stone Set(4*3cm & 5*6cm) (4*3cm) Stones are a standard size and a standard shape, which can be more convenient for some therapists to work with it Suitable for stress and tension relief / Dimension: 4*3cm & 5*6cm set of 7 These polished massage stones can be used any time and as often as you like Suitable for those who long to use computers, mobile phones or other electromagnetic radiation class equipment Note: it is a natural energy of rock, some rock have a little texture on the stone