5/16-18 standard thread hex head cap screws, also known as hex cap bolts, made of 316 stainless steel for ultimate corrosion resistance. 316 stainless steel provides the best corrosion resistance of all stainless steel fasteners. Sometimes you just need to step up the program and use a big Hex Cap bolt. Hex head cap screws or bolts have got the fastening power that you are looking for, and in marine grade 316 Stainless Steel they will resist corrosion like no other. Tighten hex head cap bolts and screws with a socket or hex wrench, which makes it easy to apply torque. Remember that Stainless Steel can sometimes Gall (seize) when tightened under load -- especially with larger size fasteners like Hex Caps. To prevent this apply a dab of Anti-seize compound before tightening the nut.