The Altra King MT is made for runners who embrace mud, rocks & burly mountain climbs & has made its mark as the quintessential king of the mud. The King MT 1.5 features a new upper with reinforced mesh & enhanced drainage features at the toes & medial midfoot, The Foot Lock™ strap has been moved medially & lower down the arch for increased comfort, & the neoprene inside the heel is softer & more secure. The awesome, grippy Vibram® outsole, 6mm lugs, & the dual nature Altra Ego™ midsole are too good to change, so we kept them the same.