The Calming Cap is a wonderful tool for easing a dog’s anxiety in high-stress situations. The calming cap reduces visual stimuli and helps dogs to remain comfortable, overcome fearfulness and increase their confidence. The single-panel sheet fabric window does not blind dogs, but simply filters their view. Try it for yourself — you’ll see that while your vision is somewhat limited, you’re still able to comfortably and assuredly make out shapes. Quality Features: • Single-panel sheer fabric allows ample vision for dogs to confidently maneuver around while reducing any provoking stimuli. • Soft fabric and elastic fit provide maximum comfort. • Two adjustable straps allow for easy on/off use. • Use with a Thundershirt when more calming is needed. X-Small Snout Circumference - 3" - 6". Distance from "between the eyes to collar - 2.5" - 5" Small Snout Circumference - 5" - 8". Distance from "between the eyes to collar - 5" - 9" Medium =Snout Circumference - 7" - 10". Distance from "between the eyes to collar - 7" - 12" Large. Snout Circumference - 9" - 12". Distance from "between the eyes to collar - 9" - 16" If unsure between sizes, go with LARGER size.