Measuring your dog is important as sizes for Dog apparel can be confusing; remember that sizes cater for the tiniest of dogs, so your 'small' Spaniel may in fact be an X Large in clothing when compared to X Small for a Teacup Chihuahua! We recommend you measure your dog using the guidelines shown and choose the size giving the most room. Remember that any clothing and especially collars should fit comfortably and snug without any restriction or tightness. Dogs come in all shapes and sizes and the information shown is for guidance only, we are happy to exchange items for alternative sizes where available. Please refer to the size chart shown for your selected product as some sizes vary between styles. If you require any assistance please contact us.