O'Neill FX-5 Firewall 5mm Dive Surfing Neoprene Black Booties with Zipper Mens 105mm O'Neill Dive Boots w/ Zipper The 5mm dive boot by O'neill is a great semi-dry cold water boot. Features 100% stretch neoprene, sealed seams and zipper to eliminate flushing, a poly fleece interior lining to wick moisture from the skin and retain heat, and a durable sole. Thickness Chart: *Water temperatures are only guidelines. Many variables such as water temperature, depth, duration, and personal water temperature tolerance will impact your comfort level. It never hurts to order a thicker boot. 5mm: 50 degreesVery Good Condition, Smoke Free Home, Fast Shipping!