Parts of a bike helmet

The materials, features, and fit of a cycling helmet directly impact the comfort and performance you feel when you ride. When looking for cycling helmets it’s important to consider which factors will or will not benefit you and your style of riding.

What are the different parts of a bike helmet?


The outer shell gives shape to your helmet. They’re usually made of thin plastic or a hard-shell like a skateboarding helmet. Shells often have reflective materials on back of helmet that can enhance visibility.

Fit system

The fit system is a series of straps and fasteners that tightens the helmet comfortably around your head, generally above your occipital lobe.

EPS liner

The inside of most helmets is often filled with expanded polystyrene foam, or EPS. This high-density foam is designed to absorb certain types of impacts and cushions your head to help protect it from certain injuries.

Chin strap

The chin strap keeps your helmet on tight, so it is less likely move off your head if impacted.

Strap divider

The strap divider allows the chin strap to fit comfortably around your ears.


A helmet’s buckle securely affixes your helmet’s straps together under your chin.

Additional bike helmet technologies

As science has come to better understand how rotational and linear impacts effect our brains, there have been technological advancements designed to help address certain head injuries. Mips and WaveCel, two examples of newer technologies offered in select Bontrager helmets, are worth considering when you are picking out a new helmet.


Mips stands for Multi-directional Impact Protection System. The Mips Brain Protection System (BPS) allows the head to move inside the helmet which may reduce the harmful rotational motion otherwise transferred to the brain.


WaveCel is a collapsible cellular structure that lines the inside of the helmet. WaveCel is a revolutionary, Bontrager-exclusive helmet technology that is designed to absorb linear and rotational energy that occur during certain helmet impacts. This Bontrager-exclusive technology disrupts the safety standards the industry has accepted for over 30 years.

Types of bike helmet fit systems

Most types of modern helmet fit systems use a dial or adjustment knob that quickly and easily lets you adjust the fit of your bike helmet with one hand.

The Boa® System

This fit system uses a dial and lace system for a precise, fine-tuned fit that’s super easy to adjust on and off the bike. You can easily secure and adjust helmet fit with just one hand. To tighten the fit, rotate the dial towards the right. To loosen the fit, rotate the dial towards the left. You can typically find this closure system on higher-end cycling helmets.


Headmaster is the fit system used inside many Bontrager helmets. Inside the helmet, small adjustments can be made to raise or lower the fit system. Simply slide the system to the side and lower or raise it to the different positions on the anchor for your preferred fit. A knob at the rear of the helmet lets you tighten or loosen the inside straps to fit the circumference of your head.

How helmet buckles work

Helmet buckles help keep your helmet securely fastened on your head. While standard buckles are still found on most helmets, newer fastening technologies, like Fidlock, are becoming more common.

Fidlock magnetic buckles

To join your straps together, just bring the two buckle pieces together until the magnetics connect and buckle is affixed to itself. To unfasten, slide the buckle pieces sideways away from each other.

Traditional buckles

To join your straps together, just bring the two buckle pieces together and listen for a click as the buckle engages. To unfasten, depress the tabs on either side of the buckle.

How helmet strap dividers work

Helmet strap dividers help ensure that your straps stay put and don't sit on top of your ears. Some helmets feature adjustable strap dividers so you can find the most comfortable strap position, while others opt for simple, fixed straps.

LockDown strap dividers

Unlock the strap divider by pulling up on the plastic tab. This allows you to move the divider up and down the helmet straps so they fit comfortably below your ears. To fasten, push the piece back into position to lock the divider into place.

Fixed/flatlock strap dividers

These plastic dividers need no adjustments. Simply pull the helmet on.

Need replacement parts?

We offer a wide variety of replacement parts for your bike helmet, including sweat pads, visors, fit systems, and more.

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