Icebreaker Men's Boxer Brief with Fly merino-wool Merino fabric in 150 All Season weight fits like skin, breathes freely and insulates warm or cool as the weather demands. When worn under other Icebreaker clothing the fiber's grain lets the fabric layers cling together and behave as one article of clothing. Buying an Icebreaker product supports socially responsible business and protects the environment. The Icebreaker Men's Boxer Brief with Fly moves with you through a full range of motion, preventing chaffing as it harnesses.