Mens Adidas long sleeve, quarter zip shirt. Size (See Measurements)

This is a preowned, in EUC, Mens Adidas Black w/white trim, long sleeve quarter zip shirt. It measure 21” from pit to pit & is 28” long. Sleeve length is 24.5” long from shoulder seam to cuff. Fabric content is 100% polyester. I just cannot read the size. Please see measurements.