Icebreaker Size Guide. You'll never worry about making a move in the Icebreaker® Departure shirt! Regular fit shirt. Woven merino wool, offers a soft hand while regulating your temperature for a comfortable wear throughout the day. Gusseted construction for full range of motion. Spread, fold over collar. Short sleeves. Button-up closure. Shirttail hemline. 100% merino wool. Machine wash cold and dry in the shade. Product measurements were taken using size MD.