These have 4 layers in the padded part of the dog protection. 1 outer layer of PUL, 2 microfibre layers and 1 mesh inner layer. 

Mesure the dog around the waist were they start to dip in at there slimmest point.

Xs fits 25.5- 30.5cm 
S fits 23-41cm 
M fits 35.5- 51cm 

Dog sanitary protection