Approximate Size Chart
Tiny: Weight 1-3 (lb) Girth 9-11 (in)
XXS: Weight 3-6 (lb) Girth 12-14 (in)
XS: Weight 5-10 (lb) Girth 14-16 (in)
S: Weight 9-16 (lb) Girth 16-18 (in)
M: Weight 15-22 (lb) Girth 18-21 (in)
L: Weight 22-32 (lb) Girth 21-24 (in)
XL: Weight 30-40 (lb) Girth 22-25 (in)
XXL: Weight 41-60 (lb) Girth 27-31 (in)
XXXL: Weight 61-75 (lb) Girth 32-36 (in)