This insole contains tourmaline and it can heated spontaneous ,and its main effect is to message the feet and keep warmit may not reach to a high temperature, because it makes people feel uncomfortableBenefitskeep warm and keep healthylong-term effect and durablewear comfortable and beautiful, does not affect work study and life;without using any energy, reliable, and eco-friendlythat is markedly heat-based products, no external power and heat.Material: Cotton,Tourmaline powder balls,Far infrared rays ballsColor: as shownSize: as shownPackage Include:1 Pair Shoes  InsoleNoteThe color is just for reference only. It may slightly different from real item.Please allow the size for 1-3cm difference due to manual messurement. Thank you!