Measure back - from base of neck to base of tail - for sizing XS = 10" (chihuahua, yorkshire terrier) Small = 12" (jack russell terrier, french bulldog) Medium = 16" (beagle, boston terrier) Large = 20" (boxer, lab) This reversible dog blanket coat features a water-resistant shell on one side and a navy fleece plaid on the other. Both sides feature reflective elements for greater visibility in low-light conditions. ThermaPet Nor'Easter Dog Coats are made with metallized polyethylene terephthalate (MPET), the same material used in space blankets. Originally developed by NASA for the US space program, MPET is scientifically designed to offer maximum warmth without weight, bulk, or the use of electricity. Our Zack & Zoey® ThermaPet™ Nor'Easter Coat in Burgundy combines advanced warming technology with a sporty design for unbeatable performance, versatility, and comfort. Solid water-resistant shell reverses to plaid fleece ThermaPet™ layer reflects dog's own body heat Reflective elements for safety in low-light conditions Adjustable touch fastener closures at neck and chest Machine washable Our best-selling Nor'Easter Dog coat now combines advanced ThermaPet™ warming technology to give extra protection against wind, chills, snow, and other elements all year long. The MPET in ThermaPet technology utilizes passive reflective heat transfer, keeping pets warm by reflecting back their own body heat. Material: 100% polyester; 100% polyester fleece; MPET inner lining gameshow