Fly High Pro X Series Tube Sac Ballast Bag 2011 – Versatility is it’s middle name; the Fly High Pro X Series Tube Sac can be used in the ski locker of your boat or on the floor just forward of the engine compartment. It’s longer and narrow enough to fit perfectly along the walkway to the bow or under side seat of V-Drive boats. You could also have the best of both worlds with one in the ski locker and one on the floor above it.