This is a super cool blue jacket. It could be called a blue suit coat. Or even a blue blazer. ANYways, it's cool, it's blue, you wear it over things...or do you!? There is a bit of give so wearing it is like tricking everyone else into thinking you're like all business and stuff when it's actually crazy comfortable and chill.
Model at left is super nice and is fixing her hair. Also, she's wearing a size small blazer. She's 5'8.5" tall (can't forget the .5!) and weighs around 135 pounds (but she doesn't have a scale so she can't be sure her exact weight at any given time, but she feels great and loves her life, so that's all that matters), if this helps assess the size that might work for you.