575 Count, 9" x1-5/8" Steel, Flat Head Square, Backer On Cement Board Screws, Serrated Head Design For Flush Seating Even At An Angle, T-25 Bit Provides For Easy 1 Handed Installation, Patented Design Allows Attaching Close To Edge N Cement Board, Drastically Reducing Fractures Or Blow Outs, Use To Attach Cement Board To Wood Or Light Gauge Steel Studs, Ideal For Use In High Moisture Areas.