Just soak in water, ring it out and pop it on. No chemicals, just simple evaporative technology. The highly absorbant mesh fabric releases body heat as the water evaporates. To 're-charge' just wet and ring out again each time it dries. 100% Polyester, Interior: 50% Rayon / 50% Polyester
Size determined by neck circumference: with your dog standing or sitting, measure around the widest part of their neck.
Small: 7 "- 11"
Medium: 12 "- 16"
Large: 17 "- 23"