Able to sustain between 80 and 100 pounds of weight, our self-tapping screws create their own thread in the process of securing the tarp mounting brackets onto your trailer's metal surface, adding greater strength and stability to the covering system protecting your cargo. We recommend drilling a 1/4" pilot hole for our 5/16 self tappers. Our 5/16 x 1 Self Tapping Bolts are designed to fasten tarp system hardware to your trailer. Commonly used in most roll tarp system installations. Compatible with all roll tarp systems. Sold in Packs of 25.