While not yet a fad, over-the-ear aero helmets are sweeping the Tour Down Under.

The Ineos Grenadiers team wears the KASK Utopia, and ear dynamics are spreading to the EF Education Easy Post team.

Harry Sweeney of the men's team, first spotted by Escape Collective, wears a wild new aero helmet from sponsor POC that looks like a mashup of the Procen time trial helmet for the road.

The radical design and time trial style of this road helmet made me think there must be a prologue or time trial stage when I first saw it, but I must have missed it somewhere.

The KASK helmet resembles a road helmet, but with an extra section over the ears; POC is a brand known for wild helmets, but this design says "hold my beer," with a visor in front and ear covers extending downward from the shell in a separate material, exhaust vents at the rear.

The POC clearly takes great inspiration from the Procen time trial helmet, but reduces some of the features to make it more suitable for road use. For example, the tail is shorter and the ear covers only come down halfway, presumably to save weight and maintain ventilation.

Like the Procen time trial helmets, there are three large vents in the frontal area and an integrated visor, which has become obsolete in recent years despite Giro Vanquish's attempts. This visor appears to be attached using three magnets on the underside of the eyebrows, which can be removed and attached to the rear of the helmet, as Sweeney did in the photo above.

The result appears to be a helmet that bridges the gap between aero helmets and time trial helmets, faster than POC's current aero road lineup, but still within the UCI rules.

There is no rule in the UCI technical rules about whether the helmet can or cannot cover the rider's ears, but it probably still plays a role in the design of the ear area.

The UCI has rules governing helmet dimensions in track and road races, presumably to limit the teardrop shape of aerofoil that was previously common in time trials.

The rulebook states:

"In road and track events, the dimensions of the helmet (including accessories) shall not exceed the following dimensions: length (L) not exceeding 450 mm, width (W) not exceeding 300 mm, height (H) not exceeding 210 mm."

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For reference, standard road helmets are approximately 160-180 mm tall, so the 210 mm height would limit the height at which the helmet can come above the ears.

It is not known at this stage; the UCI states that "commercialization will take place within 12 months of first use in competition," implying that it must be available for purchase within a year, but there are ways for brands to delay this if necessary.

In any case, more details are expected to be announced in the coming months.