These are Star Trek TOS costume short sleeve shirts! These are the voyages of the starship USS Enterprise. It's five-year mission: to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no man has gone before! These awesome TOS shirts come in costume styles of 2 of the most popular characters in the franchise's history, Captain Kirk and Science Officer Spock! Each costume short sleeve t-shirt features a top-notch embroidered Star Fleet insignia, The Command Insignia on Kirk's, and the Science Division on Spock's. The shirts are made of an ultra-soft and comfortable 60% cotton / 40% polyester fabric blend that is for wearing at any time! They are listed in regular men's sizing. The model in the photo is 5'10" and is wearing a size medium. Please See Size Chart for exact measurements These are the best!