Armpit to armpit - 21 inches. The shirt has never been worn, has been in storage for decades, and is considered deadstock since its decades old and still brand new. It has a multicolored plaid pattern all over. The shirt has a straight collar, is button front, has two chest pockets, has a square bottom hem, and is 100% rayon. The tag reads size Medium 15-15.5, and exact measurements are provided.
Actual sleeve measurement is 33.5 inches. All items that are pre-worn have been washed or dry-cleaned.