Hurtta Sun and Bug Blocker, Sand NO TWO DOGS ARE THE SAME - Dont guess on the size. Use the size chart along with the Measuring Your Dog size guide. The back length is the most important for apparel PURPOSE - The Sun & Bug Blocker is designed to protect your dog from mosquito and ticks while also blocking harmful UV rays BENEFITS -Short-haired and hairless breeds will benefit from the Sun & Bug Blocker when exposed to prolonged sunshine while all dogs can benefit from the bug protection MATERIAL  Like a fishing shirt the material is light and breathable with a rating of (UPF 40). It has a Permethrin-based repellant built in to protect your dog from biting insects FREEDOM OF MOVEMENT - Thanks to its thin and breathable material, the overall is comfortable and unobtrusive to wear. The flexible material does not restrict movement