For the hottest of days, Castelli’s Ultraleggera jersey is a very good option. There are a number of positives to it – its super-light weight, superior breathability, great feel and good wicking abilities, for example.
The jersey is remarkably light (70g for a large size) and the polypropylene mesh fabric so thin and porous that it’s almost see-through when not pressed up against your skin. On a hot day, this jersey feels great – the wind blows right through it.
Hold the jersey up to the light and it’s clear just how thin the mesh is
Wind isn't the only thing that gets through, though. While Castelli estimate the UV protection rating to be about 15, they do concede that you can get a tan through the Ultraleggera. That said, we didn't get burned while wearing the top, even on four-hour rides through the middle of sunny days.
The Ultraleggera comes in white, red and black. We tested the latter version in sunny Boulder, Colorado, and thought the colour seemed an odd choice for a top designed for extreme heat. We did feel the temperature on the shoulders, where the material was tightest while we rode. Otherwise, though, we didn’t notice any additional warmth from the jersey.
The cut is Castelli’s snug, race-oriented fit, with the somewhat longer sleeves that seem to be in fashion these days. The polypropylene is so light and stretchy that the material can’t really bind anywhere. The trim material, however, is a bit heavier, so there’s a noticeable difference in stretch at the collar and hems compared with the rest of the jersey.
The problem with the Ultraleggera, and it’s one that could be a deal-breaker for some riders, is that the super-stretchy mesh makes for terrible pockets. Anything heavier than a gel drops like a bowling ball in a pair of tights, pulling the pockets way beneath the lower hem.
Try putting a multi-tool in the pocket and it will be dragged down round your hips
Pearl Izumi recently introduced the PRO Leader jersey, which has a support structure for the pockets. Something similar – or just a less stretchy pouch material – could be the solution for the Ultraleggera.
Overall, the Ultraleggera felt great on four-hour rides when the temperature hit 100 degrees (38 in Celsius). With such great airflow, we never felt the need to unzip fully. But having to plan food stops around dainty pocket capacity is just silly.