X-Small: 7.5” L x 6.5” W / 8.75” neck circumference / fits up to 7 lbs

Small: 10.5” L x 7.75” W / 11.25” neck circumference / fits 8-13 lbs

Medium: 12” L x 9.25” W / 14” neck circumference / fits 14-22 lbs

Large: 15” L x 10.75” W / 16.5” neck circumference / fits 23-40 lbs

X-Large: 19.75” L x 13.5” W / 19” neck circumference / fits 40+ lbs