Definitely get a medium puppia.
I got medium for my two boys who are each 10 lbs and it is a little bit big on the smaller guy, but we got a size small for him originally and it was sooo small it wouldn't even strap and it was really short-bodied too.
You will love the puppia, I know I do!
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♪ Jimi | Marshall | Hendrix ♫
"When the power of love overcomes the love of power, the world shall know peace." - Hendrix