Lightweight, 4-way stretch HeatGear fabricsSuperior HeatGear moisture transport keeps you cool and dryPerformance waistbandArticulatedmesh crotch for comfort, ventilation & supportArmourBlock - Anti-odor technology90% Polyester / 10% Elastane

"O" is for "original". The O-series boxer from Under Armour is the OG of performance underwear. Under Armour was first to the game with synthetic, wicking underwear, meant for the most extreme of sports. Super moisture transportation and quick-drying fabrics make these underwear ideal for day-in, day-out wear.