Mikewrote a review of Bell Z20 MIPS Helmet on April 4, 2018
Familiarity: I've used it several times
I did a lot of research and tried a lot of helmets before I decided on the Z20, which I did mainly for the ventilation, comfort, sweat guide (which truly does work), and tech. I wanted something that would be a true all-around helmet. I essentially narrowed my search to the Synthe, and Bontrager Velocis. The Synthe seemed overpriced and dated, and I really just opted for the Z20 due to the overall attention to detail seemed to be slightly above the Velocis.
While subjective, the fit is very comfortable for me. I tried on other helmets such as the Synthe, Aro5 & 3, Bontrager Velocis, POC Octal, Specialized Prevail & Evade, Lazer Z1, and other competitors from Scott, LG, and Kask. While none of these helmets were truly uncomfortable (sans the Evade), the fit and finish and overall attention to detail of the Z20 is second to none. The overall profile of the helmet does feel a bit wider and fits a bit taller on my head, but it's marginal. I think some helmets with the Boa system may be a little more evenly distributed, but not by much.
The Sweat Guide truly works and I'm a believer. I'm a heavy sweater and suffer through Texas heat during the summer. While aero is important, suffering through sweat all over my sunglasses and my eyes as well as suffocating in 95+ degrees & high humidity are both two big factors that take the fun out of cycling for me. The retention system is very comfortable and provides an even distribution across my head. I can't speak to the tech behind the protection, but the fit and finish as stated before is definitely a couple steps above the Bell Stratus (which is almost the same helmet for much less).
In comparing to my Giro Atmos, and LG Course, ventilation is leaps and bounds above both of these. The Float Fit Race helps in airflow flowing over my head and thru the helmet.
The main pitfall of this helmet is sunglasses will not fit or stay in place in the front. The vents are too large and the pads designated for sunglasses are useless. While this is somewhat minor as sunglasses hold on fine in the back vents, I've never held my sunglasses in the back and it's a shame to have a feature designated for something that is more or less useless. There may be other pairs of sunnies that work for this feature, but my Oakley Jawbreakers and Smith Pivlock Max don't work at all.
While there are no statistics or claims to support the aero prowess, I think this helmet values ventilation over aero, differentiating itself from some others on the market.
Overall I'm very happy with this helmet. It's not perfect due to the minor annoyance of the sunglasses in the front vents, but the comfort and ventilation are great. While I can't compare to many other helmets in terms of performance, I'm still very happy with the features and overall performance of the Z20.