I bought one for my min. poodle. What works best is to fit it on the dog, pin it (loose enough to get it on and off), then remove and sew the back opening (I used machine)and the velcro tabs down and it becomes a pull-over instead. It kept the dog warm.
I bought one of these for my boxer last year because he needed something warm and it was on clearance. It fit terrible - way too tight in some places and baggy in other places. With safety pins I eventually got it to fit somewhat, at least so he could wear it around the house. This year I got it out again and can't even begin to figure out how to put it on. There are much better coats and sweaters you can get for the price.