The Optimist buoyancy bags from Optiparts are made of polyurethane coated nylon and are about half the weight and significantly stronger than buoyancy bags made of PVC or PVC coated nylon. Some Optimist buoyancy bags are available with a twist lock tube valve. This valve is attached to a piece of tubing. With this valve the bag can easily and quickly be inflated and deflated. 48 litre bags are slightly heavier than 43 litre buoyancy bags but after a capsize there is a lot less water in the boat. Twist lock tube valve. Colour red, size inflated 27 cm x 88 cm, content: 43 litre. Size deflated 41 cm x 100 cm, radius 24 cm. Please note Do not over inflate the Optimist buoyancy bags. When bags are properly filled, they will be soft to the touch. Over inflated buoyancy bags may burst when heated up by the sun or rising temperatures. Make sure there are no sharp points in your boat that would snag or puncture the buoyancy bags.