Medium-Strength Fastener—Your go-to screws for fastening most machinery and equipment. They have tensile strengths from 90,000 to 120,000 psi.

High-Strength Fastener—Commonly used to fasten components in valves, pumps, motors, and other high-stress applications. These screws have a tensile strength of 125,000 to 160,000 psi.

Steel—Unfinished steel screws are best for dry environments, since moisture will cause them to rust. They require little surface prep before applying a finish, so you can apply your own paint or coating.

Hot-Dipped Galvanized Steel—The strength of steel with the rust resistance of stainless steel. These screws are an economical alternative to 18-8 stainless steel in wet and outdoor environments, but they won't hold up to salt water and chemicals. The galvanized finish is thicker than other types of coatings, so the threads may be more likely to stick during installation. You can only mate these screws with hot-dipped galvanized nuts.

Zinc-Flake-Coated Steel—The coating is tested to extreme standards, including at least 720 hours of salt spray resistance, to hold up in wet and outdoor environments. An embedded lubricant makes these screws easier to install than corrosion-resistant-coated screws.

Grip Length—Screws with a grip length have a precisely measured unthreaded section under the head, called a grip. It's stronger than the threaded section, so you can place it in joints exposed to sideways forces.