The S38 Bladder is designed for optimum balance and comfort. Its circular bladder is compact, clean and perfect for a streamlined single tank rig. The outer shell of the S38 is made of 1600 denier nylon and 420 denier Polyurethane coated nylon internal bladder. The unit is very streamlined to both reduce drag and make it easier to pass through tight spaces. It is a no bungee design and has a lower left pull relief valve. The S38 has 38 pounds (11.3kg) of lift.