Sizing suggestion by weight:   

xxxsmall – dogs/pups under 3   lbs

xxsmall – dogs/pups 3-4   lbs

xsmall – dogs/pups 5-7   lbs

small – dogs/pups 8-11   lbs

medium – dogs/pups 12-16   lbs

large – dogs/pups 17-22   lbs

xlarge – dogs/pups 23-30   lbs