The smallest threaded rods measure less less than one-quarter of an inch. It's helpful to keep a few different sizes on hand in case of an emergency or if you aren't sure what size you need. Common sizes include 3/8", 7/16", ½", ¾" and 1 inch. You can also find larger sizes of 1¼ inch up to 3 inches. Keep in mind that the size of the threaded rod refers to the length and not the width. Some companies make threaded rods in custom sizes.
Threaded rods also come in different thread directions. The right-hand thread is the more common version, but you can also find threaded rods with a left-hand thread. A right-hand thread moves in a clockwise direction and are designed to work in fasteners. Left-handed threads move in a counter-clockwise direction and are usually used in engines and other car parts. There are also some rods that have a left hand-thread at one end and a right-hand thread at the other end.
Threaded rods come in a variety of materials, with metal finishes being the most popular. Aluminum threaded rods are the most common because these rods are lighter, but more durable than some materials. Brass rods resist corrosion and are strong, but are generally used in items that change temperature frequently. Threaded rods also come in bronze, copper, specific alloys, titanium and steel, which is regarded as the strongest type of rod.
Threaded rods are also available in different types beyond the traditional metal rods. Plastic is the most common of these rods and includes any type of material made of thermoplastics. You can also find fiber, nylon, PVC and rubber threads. These threaded rods are generally for short-term use since they don't contain the same strength and durability as metal rods.