[KazzyK810]

I have a small & a large Alex. The small is what I started with and my thinking was the small is fine for winter as she just snuggles in a ball & sleeps, but I thought the large would be less stuffy and better for summer as she has more room. Both work fine.

I think bag size depends more on the size of your dog than the weight. ZoE is no "teacup" and has turned out to be pretty long & tall, so if I were to do it over, I'd buy both in large. In fact, I'll probably be replacing my small black Alex with a large before long & selling the small.