Doggles ILS (Interchangeable Lens System). The newest Doggles with interchangeable lens sets in 9 cool colors that are sold separately. Made from rugged, high-quality materials, Doggles combine function and fashion. Protect dogs' eyes from the elements and from harmful Ultra Violet rays while adding a sporty look to any canine. Also available in other styles.
Sizing
To determine proper back strap and frame length, measure the entire head circumference across the eyes and around under the ears. To determine proper chin strap length, start measurement just under one ear, go under the chin and back up to under the other ear.

Small Back Strap and Frame Measurement 12"-20" Chin Strap Measurement 4"-8" Fits Approximate Weight 9-25 lbs

Medium Back Strap and Frame Measurement 15"-25" Chin Strap Measurement 5"-11" Fits Approximate Weight 20-50 lbs

Large Back Strap and Frame Measurement 18"-30" Chin Strap Measurement 6"-15" Fits Approximate Weight 50-75 lbs

Extra lens sets are sold separately. Extra Lens Sets for Doggles ILS come in 9 colors: Smoke, Smoke with Flash Mirror, Purple, Pink, Yellow, Clear, Blue, Solid Black and Fire Brown Driving Lens. 2 lenses per pack, easy to replace.For additional information on measurements and sizes, please ----CLICK HERE.