I bought the medium size for my 4 month puppy so it would last longer and I found it better value for money. These are great, puppy loves them and they last ages. When he started getting bored of it I microwaved it for 2 x 30 seconds and it puffed up, which made the smells really come out, but you must let it cool down as it is very hot on the inside. My cavalier has a very sensitive stomach and these don’t cause him any upset. If he chews for more than 2 hours in one go, he does have smelly pumps tho!