Hex Cap Screws are bolts with a shoulder in lengths longer then 1-1/4". They have a hexagonal head, designed to be driven by a wrench.
Commonly referred to as bolts or screws. These bolts are unique because of their threading.
Hex cap screws are fully threaded in shorter lengths (usually around up to 1-1/4 inch, depending upon the bolt diameter), and partially threaded with a shoulder beneath the fastener hex head in longer lengths.
18-8 Stainless steel hex cap screws offer protection from weather and corrosive environments. Rust resistant in fresh water environments.
For salt water environments use the 316 stainless steel version.