100% Japanese Yamamoto Neoprene
The Yamamoto #40 is 20-25% more flexible than the Yamamoto #39 we used in the past. Most experts consider Japanese neoprene to be the best in the world. In Japan Yamamoto Rubber is consider the top of the heap. Until #40 came out, #39 was considered the best around.
Besides flexibility the Yamamoto is super warm. The reason is it only absorbs 2% of it weight in water compared to 40-60% for the wetsuits from old school wetsuit companies. They are like a sponge absorbing cold water. It takes a lot of precious body heat to warm a cold water-logged wetsuit. So you get cold faster.