Buildex Backer-On #9 x 1-1/4 In. Cement Board Screw (185 Ct.)Gimlet point. No. 2 star drive prevents bit from slipping. Special ribs under the head countersink into material for flush seating. Serrated thread design reduces installation torque and provides superior holding power. Corrosion resistant finish prevents unsightly rust from bleeding into tile. Specifically designed and recommended for use with fiber cement backerboard. Common applications: Bathtub shower, countertops, floors, sink blacksplash.