Full-face helmets provide the most head coverage, followed by mountain bike and skate helmets. Road bike helmets offer the least overall protection, generally. Most of today's bike helmets are constructed with Expanded Polystyrene (EPS) foam that is only designed to withstand one significant impact.

The MIPS internal liner protects from rotational forces in case of a crash, and the EPS shell offers excellent coverage. The Radix MIPS is also one of the lightest mountain bike helmets we tested, with a large weighing just 360 grams.

Mountain bike helmets typically have more protection than road bike helmets. A mountain bike helmet covers more of the back of the head since it's more likely you'll take a tumble during a mountain bike crash. In general, mountain bike helmets provide more significant protection than road bike helmets. This also makes them heavier, though.

There are various terms for helmets that are molded in one single operation where the outer shell is bonded to the expanding foam. Some are copyrighted phrases. We long used "molded in the shell," a generic term. Others use terms like in-mold or in-molded, and Bell has a copyright on the term co-molded.