Cubitainer, 20 liters
Cubitainers come standard as the positive floatation device inside all Lasers. These containers can also be used to help older boats (1970's) where the foam blocks have become saturated with water over time.
Their pliable plastic construction makes them easy to put into place. Once inside, use a shop vac to inflate and quickly screw on the cap.
For one Laser you will need three 10L Cubitainers for the forward section, and three 20L Cubitainers for the aft.