Troxell 33-8114 Backerboard Screws 200 pcs/Tub1 1/2" Contractor grade screws for all types of underlayments and concrete backer boards. Attaches up to 1" material to wood or light gauge steel.Designed to meet or exceed all building code standards. Square drive head promotes fast driving of screws with less effort and eliminates stripped heads. Adapter bits are included. Spade bit tip starts fast and requires no pre-drilling. Hi/Lo threads pull screw in. Large head flange holds materials firmly without driving through. Under head ribs countersink for a flush fit. Corrosion resistant coating allows for interior or exterior applications.FEATURES:1 1/2" Contractor Grade ScrewsMeets or exceeds all building codes.Square drive head with inlcuded bits.No pre-drilling.Hi/Lo threads pull screw in.