SHEATH 3.0 Men's No Fly Single Pouch Boxer Brief(Patent Pending) For the SHEATH 3. 0 Zen Pouch, we decided to take what made the inaugural SHEATH design so great and give it an extra dimension of style and luxury. One of the last remaining models to feature our classic No Fly Single Pouch design, the 3. 0 combines old and new with our signature 92% Modal and 8% Elastane fabric blend and comes equipped with a stylish Aztec geometric waistband, a design courtesy of our friends at TIMEWHEEL Records.