Elco - Con-Flex - 1/2" Diameter HFH, Hex Washer Head with Locking Serration (50 Per Box) (Click for Sizes/Weight)Elco ConFlex Masonry Screws Enhanced ductility allows use in demanding exterior applications Con Flex masonry screws are engineered to provide high pull out and shear values with virtual immunity to brittle failures. _ ConFlex 3 8" and 1 2" diameter threaded fasteners engineered by Elco Construction Products provide high performance in masonry and concrete, even in exterior applications. Hex washer head with locking serrations prevents back out.