SHEATH 4.0 Bamboo Men's Dual Pouch Boxer Brief SHEATH UNDERWEAR Sheath 4.0 Men's Dual Pouch Underwear SHEATH UNDERWEAR SHEATH 4.0 Bamboo Men's Dual Pouch Boxer Brief SHEATH UNDERWEAR SHEATH 4.0 AirFlow Men's Dual Pouch Boxer Brief SHEATH UNDERWEAR Sheath 4.0 Dual Pouch Boxer Brief Purple (S) SHEATH Touch of Modern SHEATH 4.0 Men's Dual Pouch Boxer Brief Gray (M) Sheath Underwear. (Patent Pending) Based on the functional design of the SHEATH 4. 0 Dual Pouch Boxer Brief, our AirFlow series takes the 4. 0s comfort and performance to a new level with the unprecedented flexibility and breathability of our AirFlow Polyamide Mesh blend.