#1 square drive trim head

It has a four sided square head at one end and a cup-shaped indentation at the other end

With superior holding power

3/8-24 x 2 1/4 L9 Hex Cap Screw Yellow Zinc Plated Domestic USA (50)

29/32 x 6 Reduced Shank Drill Bit (1/2 Shank)

10-16 x 5 Strong-Point Phillips Bugle Head Self Drilling Drywall Screw Zinc Plated (500) 3/4-10 Hex Cap Screws 18-8 Stainless Steel #1 square drive trim headThis 500 piece set of zinc plated 10 16 x 5 Phillips Bugle Head self drilling drywall screws are designed for impact drivers for quick application into a wide range of materials, and their strong point head minimizes power required for installation.