I am absolutely tickled with this purchase!  I have been wanting a black blazer for quite awhile, as it is a great clothing staple for the workplace.  I ordered size M.  I am 5'6" and about 130 lbs, and my bra size is 36A.  The blazer fit perfectly!  I am especially pleased that the sleeves are long enough; far too often, jacket sleeves awkwardly stop short of the wrists.  This blazer is a wonderful addition to my wardrobe and was definitely worth the $20.  You should give it a shot!