Barbell collars are made from a range of materials, commonly including steel (spring steel and steel alloys), cast iron, aluminum, plastics and nylon resins, polyurethane, elastomer/rubber components, and chrome finishes.
Product details list collars sized for common bar diameters: standard 1" (25 mm) bars, 30 mm (about 1.18"), and 2" (50 mm) Olympic bars.
Protective features noted in product details include soft elastomer or injection-molded pressure pads, rubber linings or gaskets, and corrosion-resistant finishes such as polished chrome to help prevent scratches and rust.
Many listings emphasize quick installation and removal: spring-clip collars clamp on and off rapidly, quick-lock latches and quick-release clips secure plates very quickly, and some Lock-Jaw/unibody designs allow fast adjustments between sets.
Some listings—particularly certain Olympic spring-clip collars—describe a low-profile design intended not to interfere with lifts. Look for the phrase “low-profile” or similar language in the product details if this is important to you.
