GRK’s R4™ Multi-Purpose 305 stainless steel screws are designed for applications that require superior corrosion resistance in exterior environments with high moisture content such as docks, boardwalks, and piers on lakes. Recommended for use with cedar, redwood and other naturally protected wood species that have a higher acid content. R4 305 stainless steel screws are recommended for applications located more than 1 mile from the coast.