Assos Equipe Thermobooster P1

The Assos Equipe Thermobooster P1 solves a problem most riders know well: the temperature window where a short-sleeve jersey is too cold and a full jacket is too warm. Assos built it to work as either a standalone long-sleeve jersey or a base layer under a shell, covering a claimed range of roughly 54-70°F. That range covers a lot of shoulder-season riding, and it's the reason this piece sits between base layer and jersey in Assos's Equipe lineup rather than fitting neatly into one category.

The body uses Assos's SENS Air Plus fabric with Hyperlight insulation, a lightweight construction chosen for breathability first and warmth second — it's built to keep a rider from getting cold without trapping heat once the effort level climbs. The sleeves switch to 575CX, the same fabric Assos uses on its RS Shell Jersey S11 aero jersey, which keeps the arms close-fitting and low-drag rather than adding bulk where it isn't needed. A two-way zip runs the front, letting a rider open the collar for airflow on a climb and close it back down on the descent, and the extended collar itself carries soft insulation designed to regulate warmth at the neck without needing to touch the zipper at all.

Fit follows Assos's AEPD 11 racingFit — a close, second-skin cut built around WorldTour rider feedback rather than a relaxed recreational fit. The cuffs and hem use a raw-cut finish instead of a bound edge, which keeps the layer flat and low-profile under a jacket or shell where bulky seams would otherwise create pressure points or bunching. Two lightweight mesh pockets on the back give it enough storage to function as a real jersey on its own in the right conditions, not just a layer meant to disappear under something else. For a rider building out a shoulder-season kit, the Thermobooster P1 is designed to be the one piece that moves between base layer and jersey duty depending on how the ride starts and how it ends.