For time trials (and so triathlons) an aero helmet adds some serious time savings. There are many out there, and I'm happy that nowadays the helmets with long tails are going out of style.
I picked the Wing 57 TT helmet because it had been tested at many Ironman and tri events, and because the wind tunnel results seemed to suggest it was fast. They claim it's the fastest helmet on the market. I also thought it looked good, and it was one of the few helmets that offered a no ventilation (maximum aero) set up. Because no time trial I'm going to do will last longer than an hour, any reduced heat/sweat advantage would be minimal. I also wouldn't wear this on any training rides (that would look silly). And anyway, if you're worried about being comfortable during a time trial you're probably not going fast enough.
SPECS: $499 / 320g
IN THE BOX: I like that this came with numerous ventilation options. It also came with a helmet bag, and a good amount of literature.
VISOR: I like this visor. I think because of their experience with glasses, they have access to high quality lenses and materials. I've never had an issue with fogging up or being blinded by the sun. They are easy to clean after the sweaty mess that usually comes along with TTing.
FIT: It fits great on my head. Nice and snug. I like the boa-style tightening and loosening mechanism at the back of the helmet, and the chin straps are high quality like they are on all Rudy Project helmets I've owned.
AERODYNAMICS: I have
AERODYNAMICS: I don't have a wind tunnel, but Rudy Project claims "shape of Wing57 provides all the benefits of NACA (National Advisory Committee For Aeronautics) wing shapes and avoids wasting the energy that is naturally lost in rending the air." They also claim "Inspired by sharks, the crown of the Wing57™ time trial helmet converts sideways forces into forward propulsion. In the event of cross winds it delivers all the advantages of a long-tailed helmet without the relative negative repercussions on the front."
ON THE ROAD: I was going from a road helmet to this, so yes it felt fast. Like, very noticeably. I felt like I could feel the results of all the Rudy claims, but there's no way I can prove this scientifically. When the wind changed directions, I could feel the air on the back of my neck switch from one side to another.
My teammates have borrowed my helmet for TTs and have all given positive reviews and plan to get their own at some point.
PROS: Fast. Looks good. No long tail. Offers fully TT no vent option. Comfortable fit.
RECOMMEND? I would recommend this helmet. The only downside is the price tag, but everything in the TT realm seems a little expensive to me. If I was to go after a cheap option I would probably just get something used, maybe a GIRO. But if you're getting something new I can def recommend this.