Sea Hawk AF-33, Blue, quart, is a harder ablative anti-foulant, for a more durable finish on all types of vessels. On workboats or daysailers, a multi-season formula for a single season price. AF-33 may be used on all types of vessels and delivers dependable performance. Highest grade of cuprous oxide available (more potent active ingredient) - Harder ablative finish - Better color consistency for color matching - Consistent viscosity = better flow and rolling ability - Lloyd's Registered.