This Vintage Star Wars The Empire Strikes Back Cotton T-shirt in size M/L is a black short sleeve tee featuring characters like Stormtrooper, Darth Vader, and iconic symbols from the Star Wars franchise. Made from a comfortable polyester and cotton blend with a crew neck and regular fit, it is perfect for everyday wear. The graphic print adds a touch of nostalgia for fans of the movies, making it a must-have for any Star Wars enthusiast. Machine washable and easy to care for, this shirt is a timeless piece that can be worn throughout the year.
The tag shows a size Large but I would say if this shirt is for a man it really is a size medium. 
It would be a teenager size large or a womans size large .

Here are the measurements
From underarm to underarm is 24 inches across
It is 100% cotton

Please feel free to ask questions