The Manifest is Giro's newest mountain bike helmet, with an extensive list of features that put it in the top tier of their trail-oriented offerings.

Along with a light weight and generous ventilation, the helmet has Giro's Spherical technology, which uses two separate layers of foam connected by elastomers that allow the two layers to move independently. The idea is that during a crash the outer layer is able to rotate enough to help dissipate a portion of the impact force, reducing the amount of stress that reaches the brain. It's a similar design to what's used in the Tyrant helmet, but in a much airier package.


Let's start with the Manifest's safety features. After all, that's what really matters – how many vents there are is a secondary concern compared to what a helmet's designed to do when your head smacks into the ground.

The Manifest has two separate EPS (expanded polystyrene) portions that are joined with elastomers. Take a look at the helmet featured in this review – you'll notice the darker grey bottom layer, and the olive green layer that sits on top. The bottom layer uses a softer foam to help dissipate slower speed impacts, while the outer layer has a higher density foam for dealing with higher speed hits. In the event of a crash, the outer layer is designed to move, pulling on the elastomers and sliding on the plastic coated inner layer. It doesn't take much force to move the two layers, but the elastomers are strong enough to keep the layers from shifting too much during normal riding conditions.

It's a similar concept to a traditional MIPS liner, but this design moves the plastic slip plane away from a rider's head, which helps create a more comfortable helmet. The ball-and-socket design was created in-house by Giro, and MIPS helped with the integration of the slip plane and elastomers.

In order to achieve their ventilation goals without compromising the helmet's structural integrity, Giro's designers equipped the Manifest with a polycarbonate reinforcing arch that runs through the center of the helmet. Ready for a new acronym? The feature is called the AURA, where AURA stands for Aerodynamic, Unbreakable, Reinforcing, Architecture.

Silly acronym aside, that arch does allow for an impressively open and well-ventilated design. There are 19 vents, along with internal channeling, and Giro say that it's 7-percent cooler than the Montaro MIPS, and nearly as cool as their Aether road helmet.

Other features include a FidLoc magnetic chin buckle, a ratcheting dial to adjust the fit, and an adjustable visor without any fixed positions – it moves up and down evenly, which makes it less likely that you'll end up with one side higher than the other, a fashion faux pas that's most commonly seen on riders who ride alone, myself included.

A textured rubber strip along the bike of the helmet helps keep goggle straps from slipping, and there's also pieces of rubber that hold sunglass arms in place when they're not in use. Flip them upside down, stick them in from the front of the helmet and they won't budge even on rough bits of trail.

Ride Impressions

As always, helmet fit is a personal affair. What fits my head may not fit yours, and vice versa, but I found the Manifest to be very comfortable, free of any pressure points or other distractions. For reference, my head shape is more oval than round. 

The Roc Loc ratcheting dial is easy to adjust with one hand, and the middle of the three vertical height positions worked best for me. There haven't been any clearance issues with sunglasses, and the top-of-helmet storage works as intended. Even on chunky climbs, or rougher downhills where I forgot to put them back on, my glasses stayed in place. Depending on the sunglasses' arm thickness the pressure on the top of my head was noticeable after a while; storing them up top works best for shorter climbs or traverses.

It's still spring time here in the Pacific Northwest, which means I haven't tried the Manifest out in temperatures above 65° F (18° C). Many of my rides were very humid, though, with long, slow speed climbs, so I did get an idea of how well it manages moisture. At speeds faster than a crawl the ventilation works very well – there's plenty of airflow, which kept the top of my head nice and cool. 

The overall fit of the Manifest was excellent, as was the level of venting...