Product Description 25 Pack, 1.5", Strong Drive SDS Structural Wood Screws, Designed For Installation In Simpson Strong Tie Connectors As Well As Wood To Wood Applications, Double Barrier Coating For Exterior & Treated-Wood Applications, Identification Stamped Into The Head With Length, Low Speed 1/2" Drill With A 3/8" Hex Driver Is The Recommended Tool For Installation. From the Manufacturer Simpson Strong Tie SDS Structural Wood Screws are 1/4-Inch diameter high-strength structural wood screws are ideal for various connector installations as well as wood-to-wood applications.