GRK Fasteners 19/64 in. X 5 in. L Star Bugle Head W-Cut Concrete ScrewsCaliburn Concrete screws are professionally engineered fasteners with a patented thread design for ease of driving the screw in concrete and similar applications. Available in three different head designs for multiple applications. Caliburn, Caliburn PH and Caliburn XL are Climatek coated for high corrosion resistance. Caliburns uncompromised draw and pullout strength make it possible to be used in jobs which previously required an anchor. The screws