Now that we have covered the confusion over the Heartgard, it is time to get even more confused about the Frontline flea and tick protection, because the weight parameters are different!
The small size is for 5 to 23 pounds in weight, NOT 25 as with the Heartgard. 5 to 22 pounds
http://www.amazon.com/gp/product/B00008DFGY/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B00008DFGY&linkCode=as2&tag=cockers-20&linkId=Y4WDPILKOQHKENS3
So think T for tiny terrier on the box.