Collar: 2 mmThe collar is made of a single layer material which has as great advantage to optionally be able to cut it with scissors to your personal perfect fit. The collar fits well and provides minimal inlet of water and prevents chafing. The closure on the rear is reversed*: the reason being that, in the unlikely event the suit is closed incorrectly, only the soft Velcro will touch the skin. We are fully convinced that our wetsuits (all models) are free of chafing. Shoulders and armpits: 2.5mmThe shoulders are made of a 2.5mm smooth skin stretch neoprene. The armpit is made of a 4-way stretch nylon that not only feels soft but is also very durable. Main upper chest panel: 4.5mm The 4.5mm thick main chest panel ensures buoyancy, which makes you go faster and gives you a better lying position in the water, delaying the onset of fatigue. From the upper leg panels: 3.5mmIn order to support the legs from sinking but still providing the freedom to run in the upper leg panels are 3.5mm thick for enough buoyancy to swim Breast stroke and Free style. The lower upper leg panels are made out of 4-way stretch nylon to give that extra freedom to run in and get in and ot of the suit even more easy. Back panels: 3.5mmThe back panels are not only there in order to ensure extra buoyancy, but they are an extension of the shoulders as well. This is why 3.5mm was selected with 4-way Super Stretch lining in order to obtain more freedom of movement as well as the additional buoyancy. 2x YKK zipThe zips have a metal runner, which ensures gradual opening and closing. Following a survey held among our Dare2Tri followers, we decided to have the zip closing from the bottom up. The vast majority indicated this is to be preferred to a top to bottom zip.