The HL4 driver features an all new sloped crown design that is deeper from face to back. No skirt where the sole plate meets the crown equates to a 12% increase in MOI over the previous Hot Launch drivers. This new design makes for an extremely high Moment of Inertia above 5000 grams per cubic centimeter. Moment of Inertia is a measure of a body’s resistance to angular acceleration or twisting, meaning that the HL4 is a more stable driver. This higher MOI will increase ball speed on miss-hits and will keep shots straighter.