Lower Volume: TruFit boots have less volume over the instep. This reduces excess water in the boots which makes them warmer. It also makes it easier to get in and out of your fins. Trufit Sole: Comes with built in arch support and a heel cup. The arch keeps the foot in a natural position which applies more power to your kicks and comfort when you re on land. The heel cup supports natural padding in your heel to absorb shock when walking.