Trek Cap. Made for life out in the nature, the Trek Cap provides comfort and breathability during sunny weather hikes, treks and walks. Highly stretchable, the trek cap is the cap-shaped sun protection alternative to summer trekking hats. Enjoy mountains and outdoor life to the top with the new mountain caps and hats by BUFF. high-technology and BUFF quality blend together in a pure outdoor collection. Created in a variety of shapes, each of the products in our Mountain Line Collection offers a specific set of features, all in BUFF style. BUFF Mountain Line products are designed for sun protection and performance while hiking, trekking or enjoying a walk in the forest.