Pack Baseball Cap. Style and functionality go hand in hand with this new BUFF® design. This Pack Baseball Cap is crafted with the best features of baseball and pack caps, providing protection from the sun. It can be stored in your bag without losing its shape. Being trendy and practical is possible. - Crown: 60% cotton, 40% nylon; Visor: 60% cotton, 40% nylon; Under visor: 97% polyester, 3% elastane; Adjustable strap: 60% cotton, 40% nylon; Inner sweatband: 100% polyester.