Sizes are available in x-small (up to 8"), small (8"-12"), medium (12"-16"), large (16"-20"), x-large (20"-24") and xx-large (24"-28"). Measure length of pet's back from the base of the neck to the base of the tail. If the measurement is between sizes, we recommend going up one size. Also, if pet has a stout build, a deep chest, or is overweight, we recommend going up a minimum of one size for proper fit. If the dog is long-backed, like a Dachshund, a smaller size is recommended. Please click on the product image to get a large view and sizing guide.