Field Guard Sizing GuideLineup of dogs of different breeds and sizes.

Good Fit ⇒ Comfort ⇒ Easy Acceptance!

A well-fitted Field Guard is easily accepted by most dogs because it is engineered for comfort. The correct size allows room for the dog to open his mouth and pant, and for air circulation around the face that is necessary for cooling. If you want the best fit for your dog, use these measuring instructions for exact sizing.

Updates to 'O' Sizes

Before March 2022, dogs with furry faces, extra long ears, or a blocky heads required an “O” size to allow space for necessary air circulation and cooling. All other dogs were able to utilize our regular size. With the announcement of our new sizes, we have eliminated the 'O' size.

The chart below is the New Size Guide Chart for all sizes in stock. Note that PUPPY size is and has always been based on current head length.

Size Chart

Measure your dog for correct sizing. Breed examples are just a rough guideline. If your dog's measurements are on the borderline between sizes: for XXS & XS, XS & S choose the smaller size; for S & M, M&L, L & XL choose the larger size.

Dog Size Chart based on Head Length
Size Head Length Breed Examples
XXS 5½-7 in (14-18 cm) Chihuahua, Miniature Dachshund, Cavalier (sm), Poodles & Doodles (toy/miniature), Pug (sm), (not for dogs <9 lbs)
XS 7-8¼ in (18-21 cm) Cairn Terrier, Jack Russel, Norwich Terrier, Cavalier, Pug, French Bulldog
S 8¼-9½ in (21-24 cm) Beagle, Brittany Spaniel, Jack Russell, Sheltie, Boxer, Pit Bull, Doodle
M 9½-11½ in (24-29 cm) Australian Shepherd, Border Collie, Vizsla, Labrador, Greyhound, Basset Hound, Bernese (sm), Doodle (std), Rottweiler, English Lab, English Bulldog, Wheaton Terrier, Scottish Terrier
L 11½-13½ in (29-34 cm) Doberman, German Shepherd, Weimaraner, Bloodhound, Pyrenees, Mastiff
XL 13½-15½ in (34-39 cm) Great Dane, Irish Wolfhound, Bloodhound, Great Pyrenees, Mastiff, Saint Bernard


Need Help Choosing a Size? For additional assistance, email us at Please include head length, weight, and a photo of your dog.

Adjusting for Fit The correct fit is as important as size for your dog's comfort and acceptance of the Field Guard. Download the OutFox Comfort Guide for how to create the best fit for your dog.