Different helmet models are meant to protect in different ways. A half shell protects the top of the head. A 3/4 protects the top, back, and side of the head but leaves the face uncovered. A full face covers the entire head and face.
They All have a few things in common such as: A hard outer shell that is meant to resist a certain degree of impact and deflect rocks or other road debris. A liner on the inside separating the shell or styrofoam and the rider's head. A connection device that secures the helmet straps. Sizing or comfort pads to make the helmet tolerable on long rides. Some helmets incorporate this into the actual liner.
The shell of the helmet is hard and resistant to cracks. Most are made out of a hard plastic, polycarbonate, or fiberglass. Some of the more exotic models are actually made from carbon fiber or even kevlar. Older or traditional helmets work by compressing or crumpling somewhat into a styrofoam to prevent the force of impact from reaching the rider's head.
The lining of the helmet is final layer of protection before your head. Some liners are better than others. Some may use a terry cloth liner while other may use a moisture resistant memory foam. The higher priced helmets usually have sizing or comfort pads to absorb even more energy.
A strong strap connection is extremely important to secure your helmet in the event of an accident. D-rings are common. The quick release buckle type are also common these days. Just make sure to stay away from flimsy plastic connectors. Look for a military spec quick disconnect made of thick polymer.
A good strap connection is essential for helmet retention in the event of a crash. The buckle type should be made of a high grade polymer much like a military spec quick disconnect. D-rings are also fine as long as you have the straps tight enough.
See a Facebook page about Carbon Fiber Motocycle Helmets.
