Under Armour Kids - Boxer Brief Underwear (Big Kid). Color Castlerock. On sale for $21.58. MSRP $26.00.. 5.0 out of 5 starsAdd to favorites. 0 people have favorited this+6Brand NameUnder Armour KidsProduct NameBoxer Brief Underwear (Big Kid)ColorCastlerockPrice$21.58MSRP: $26.00Rating5Rated 5 stars out of 5(5)