This is the Heartgard 26-50 pounds pack so you can identify it easily.
http://www.amazon.com/gp/product/B00SYO2USE/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B00SYO2USE&linkCode=as2&tag=cockers-20&linkId=C3KYVHVUOY467SLX
Think GREEN for greater. Many male cocker spaniels and some pudgy females will be in this weight range. At the upper end of the range, we will have some smaller English cocker spaniels, such as females.