The quality is perfect, I purchased a 4T for my almost 3.5 year old boy, and it is just slightly long after I adjust the straps for the shortest setting.  My son is 37 inches tall and about 36lbs.  I am happy with the slightly long length because it will fit him for another season.  That said, if you are wanting a near perfect fit, and you have a tall 3 year old this would be perfect, and if you have an average size 4 year old, this too would be perfect for a boy or a girl.  I would say this product is true to size.