I bought one of the original aboistops about 15 years ago. In those days they only sold one size, the larger one. It worked very well but I was always afraid that it was very heavy for our small terrier. When I saw that the now produced a compact version I decided to buy it. I have been very disappointed. Within 6 weeks it stopped working properly. The reservoir becomes empty very quickly and when you try to refill it the fluid just drips out the bottom. It is as though the reservoir is full of air and won't let the fluid in.