The following sizes description and sizes were described on picture just as references, please refer to the actual subject.

Small Size - (About Suitable Weight for Pet 19 lb-38 lb).

Size S fits for American Eskimo Dog,Beagles,Kerry Blue Terrier,Kooikerhondjes,and Puli,miniature Australian Shepard, etc.
- Chest Size:22.8"- 25.2"
- Belly Size:13.4"- 20.1"
- Neck Size:14.2"- 16.1"
Medium Size - (About Suitable Weight for Pet 39 lb- 60 lb)

Size M fits for Samoyed,Siberian

Husky,Goldendoodle,Malinois,Bearded Collie,and American Staffordshire Terrier, etc.
- Chest Size:27.6"- 31.9"
- Belly Size:16.1"- 21.7"
- Neck Size:20.0"- 23.6"
Large Size - (About Suitable Weight for Pet 61 lb- 100 lb)
Size L fits for Doberman,German
Shepherd,Schnauzer,Labrador Retriever,Old English Sheepdog,and Rottweiler,etc.
- Chest Size:31.0"- 35.0"
- Belly Size:26.0"-39.0"
- Neck Size:24.0"-31.0"
WEIGHT AND ACCOMODATE
S:9.9 oz, Can accomodate under 1.5 lb
M:11.6 oz, Can accomodate under 2.5 lb
L:13.4 oz, Can accomodate under 3.5 lb
NOTE:
- If you want to get a suitable backpack for your dog,please take for reference on above measurements correspond to chest,belly,neck size.
- Waterproof design.But If it rains,it will get wet.
- Be careful, the sharp items like branches ,to prevent scratching.
- Don't put something overweight in the pack, otherwise your pets will uncomfortable.

• Durable,Made of high quality 600D double polyester material
• Perfect 3 adjustable straps and neck circumferenc,Breathable harness bring your loved dog comfortable feelings
• Many choices,3 size(S/M/L) and 4 color(Black/Blue/Orange/Red) for different size dog & individual's color preference
• Each side has one convenient pocket for carrying food and water
• Perfect for walking,shopping, hiking and jogging, and gear for you and your pet wherever you go

Durable,Made of high quality 600D double polyester materialwelkey