Both 4-Speed propellers are investment-cast from 15-5-grade virgin stainless steel, balanced and heat-treated. They are available in right- and left-hand rotations in 2-inch pitch increments from 24 to 34 inches. The 4-Speed sterndrive is 15.5 inches in diameter and the 4-Speed OB/FX is available in 14.75 or 15.25 inches. The larger diameters help the blades hook up in aerated water produced by stepped and air-entrapment hulls, and help with drives mounted at aggressive X-dimensions and outboards with a high installation. The blade design is key for the performance and efficiency, using variable cord lengths throughout the blade area. The cord length is the distance between the leading edge and trailing edge of the blade at any given point along the blade. Where the blade attaches to the hub, a long cord length helps get the boat on plane. Once up and running, the prop needs less surface area meeting the water to maintain top speeds. An extended exhaust tube length helps improve planing times and acceleration, but the tube isn’t flared at the end, meaning reduced drag and increased top-end speed. The 4-Speed OB/FX has an adjusted exhaust tube to allow for a little ventilation when planing.