Constructed from a seamless polyethylene shell filled with low-density EPS foam. The shell is infused with UV inhibitors and has a minimum wall thickness of 0.15". Unaffected by saltwater, gasoline, oil and most chemicals. Flat top has a flange with eight 1/2" holes for fasteners. Freeboard depends on how heavily the float is loaded—typically, floats are submerged about 4" on an unloaded dock. Can be shipped UPS.