Since its introduction, the O'Neill Psycho Tech 4/3+ Back zip wetsuit has been a go-to suit for many cold water surfers. Continuing the legacy, the suit provides the warmth and flexibility to keep you charging. The Psycho Tech utilizes TB4 neoprene. TB4 includes graphene fibers that increase the material's durability and thermal properties. The patented Z.E.N. Zip Closure includes extra material between the zipper and your back for maximum comfort and optimal seal. You'll be stoked about the updated materials and construction if you are looking for the warmest and stretchiest back zip suit.