Most TT's and triathlons take place anywhere from late spring through early fall, often on some of the hottest days of the year. A TT/tri-specific lid can certainly speed up your ride, but not if it isn't built with enough ventilation to keep you cool. How to make "aero" helmets that save watts without leaving cyclists trapped inside a stifling bubble is a recurring challenge for helmet manufacturers. That's why we're impressed with the Giro Aerohead MIPS Helmet's wind-cheating profile and efficient venting system, which incorporates more cooling channels than the Aerohead Ultimate and features the added impact absorbtion of Multi-directional Impact Protection System (MIPS). On the outside, the Aerohead uses a pretty standard In-Mold construction; polycarbonate fused to EPS foam acts as an initial shock-absorbing layer and keeps the helmet's efficient profile intact. Inside, a MIPS liner feels barely perceptible as you ride, but It's a technology that's becoming ubiquitous in helmets across disciplines because it rotates slightly upon impact to redirect energy generated by certain impacts.