Onsen 4/3 FZ FullOur Onsen 4 3 is the one suit quiver killer. The geometric cell structure of Yamamoto #40 in our Onsen wetsuits are 98% water impermeable and locks in body heat, which allows this 4 3 exceptionally comfort and warmth into water temps that could warrant a 5 4. Onsen wetsuits are constructed with 100% Yamamoto #40 neoprene. Every detail has been tested in the harshest of conditions and designed utilizing comprehensive research and development that