Three-quarter helmets like this new Bluegrass Jetro have forged a bit of a category of their own, sitting between regular half shell lids and the best lightweight full-face enduro helmets. The trend stems from riders who want a little bit more protection but without that hemmed in or overheated feeling from a full-face lid.

This extended coverage is especially reassuring when you’re descending aggressively, and some of the best mountain bike helmets around adopt this approach. Sure, they’re a niche product, but I find that when I’m somewhere with both plenty of pedalling and gnarly descents, or e-bike riding where absolute weight saving and cooling isn’t my number one priority, they’re spot on.

The Bluegrass Jetro is a good-looking and trendy helmet with a bit of extra warmth and protection.

Anyone that’s been around cycling or BMX a while will know helmets like this aren’t actually new though. As far back as the 1980s, BMXers searching for extra protection without cooking up wore similar-looking ‘helmets with sides on’ from Troy Lee, Echo, JT Racing and Bell.

And, just like these BMX lids, Bluegrass’s Jetro offers extra protection for gnarlier tracks, but still allows perfect vision at all angles (and slower speeds) and maximum air flow for cooling and breathing compared to a full face. The extra protection here covers the sides and back of the head as well as the sides of the jaw and upper cheekbones. It stops short of the full front chin guard to close the rider in and bounce back all that hot air being generated by breathing out while working hard.

The Jetro is certified to the higher e-bike safety standard.

Design and specifications

The Jetro borrows heavily in styling and safety tech from the Bluegrass Vanguard full face lightweight enduro lid and comes with NTA 8776 certification. That’s the standard for e-bike helmets covering a higher speed and impact rating, and the best full face and convertible helmets.

An EPS layer inside extends over the full helmet, not just the top and back. Bluegrass claims its design, fusing the EPS into the outer shell, lets impact energy dissipate more “significantly”. This design is essentially much the same as other brands use, and there are no multi-foam densities or special internal shapings advertised here that other manufacturers claim absorb more impact energy.

One claim about protection levels that’s definitely not just from the brand, however, comes courtesy of the prestigious US Virginia Tech Helmet Lab. The Jetro has been awarded its highest 5-star rating, which means it exceeds other standards of helmet safety in both linear and rotational impacts. It also means the outer shell has endured bigger impacts at both the back and the temples, which are the two most sensitive brain areas to damage.

Mips rotational protection is standard fit on the Bluegrass Jetro 3/4 helmet.

Part of this result is presumably down to the popular MIPS technology that protects against glancing blows, which you’re likely familiar with by now. Another aspect of the protection rating must reflect the extra weight and shell/padding thickness here, as this is definitely at the heftier end of the spectrum for the category. For reference, Fox’s popular Dropframe helmet is over 200g lighter, at 391g, whereas the Jetro’s 595g is actually closer to many lightweight full face enduro lids.

The Fidlock buckle makes fastening the chinstrap a doddle.

To me the Bluegrass helmet looks great, and uses a visor that forms an integrated part of the lid, but it’s flexible and can breakaway in the event of an impact, and there’s also a fast-to-use Fidlock magnetic chin strap clasp.

The fully wrapped outer shell has plenty of wide vents all over the surface with 21 in total including the cheek and ear sections. There are effective internal air channels too, helping air flow through the interior while moving along and exhale heat out the back.

There’s an easy-to-use retention dial at the back of the helmet for customising the fit.

Jetro uses Bluegrass’s Safe-T Heta retention system, which has three vertical height positions on the rear retention dial and the lid is available in three sizes (S, M and L), so should fit most riders. Adjustable C-Shaped cheek pads also tune fit to different face shapes and widths, which I found worked really well.

Performance

Picking up the Jetro, I immediately noticed it’s much heavier than a regular open face lid. Once in place, however, it wears its weight very well and feels balanced, stable and comfortable. On top of feeling lighter than advertised, ventilation and cooling is excellent too, to the extent I’d argue it’s the best ventilated helmet of its kind I’ve tried so far.

Bluegrass has done an effective job designing the cooling on the Jetro.

The key to the superb cooling and breezy feel appears to be two distinct channels than funnel air along the temples and over the top of my ears (much like Sweet Protection Trailblazer helmet). These combine with large open vents on the cheeks to prevent too much heat build-up or any excessive sweatiness on the face compared to similar helmets I’ve tried.

These effective air channels really pumped air over the brow on both sides while I was moving, and exhaust hotter, stuffier, air out the back. Combined with the big ports on top, the overall design in terms of ventilation all works great and really stopped my face and scalp getting too hot and sticky, even on warmer days.

Another big Bluegrass win is the internal shaping and snug fit around all the contact points on my head and face. The Jetro has a very reassuring, enveloping hold with a deep dish and is extremely comfortable with padding in all the right places and no tight spots. This excellent fit extends to how stable it is too, and I found it remained rock-solid even on really rough tracks. The Jetro never tipped forward or bounced and stayed really firmly locked-on while riding.

One of the other main advantages here is the unrestricted field of vision, just as I’d enjoy wearing an open face. No helmet pieces or edges come into peripheral vision at the sides, so I could really scan the trail ahead, and I found it also played nicely with two different brands of goggles (POC and Smith). There was also no pressure at the brow forcing my goggles down the bridge of my nose like some lids do.

Cheek pads help keep the Jetro stable.

Yes, you can get a full-face lightweight enduro lid for around 25g more than this Jetro from brands like iXS, but even the best ventilated full coverage helmets will be hotter. You’ll also have a chinbar in your line of sight. This thing instead feels like a much safer and reassuring open face, ideal for when you’re not looking for maximum grid protection. (Or those riders like me who long ago smashed their front teeth out!)