Assos says that its updated Equipe ThermoBooster P1 is designed for rides that start cold and finish warm, but are somewhere in between in the interim.That sounds like most rides in the UK, even during most summers and particularly now the heatwave is officially declared over. Its also claimed to be a good option for longer, cooler descents and Assos quotes a 12oC to 21oC temperature range.The ThermoBooster P1 is a sleeved top that it says bridges the gap between a jersey and a jacket. Its packable and has a close fit so its still aerodynamic, so Assos says its suitable for racing. It can be used as a mid-layer when its colder or as an outer layer when its not too chilly.Lighter than its predecessor Assos says that the ThermoBooster P1 provides packable insulation for mixed temperature rides. The ThermoBooster P1 is made of breathable lightweight Sens Air Plus fabric with Hyperlight insulation, while the sleeves are constructed from close-fitting 575CX fabric. Theyre the same fabrics as Assos uses in its RS Shell Jersey S11 and it says that the updated jacket is now lighter weight than its predecessor. A two-way zip allows airflow regulation when riding. The jacket includes two mesh rear pockets, reflectives on the shoulders and a two-way zip to regulate airflow, so its geared up for use as an outer layer.The new Equipe ThermBooster P1 has a unisex fit and is available in sizes XS to 3XL. It comes in one colour, Kosimo Granit, and is priced at 175 / $235 / 200.How does it compare to the Castelli Perfetto and Do.di.ci? The Castelli Do.di.ci offers windproofing without water resistance in a low weight piece. Castelli Although theres no shortage of wind resistant, lightly insulated jackets, the ThermoBooster P1s nearest competitor looks to be the Castelli Do.di.ci.As with the ThermoBooster P1, the Do.di.ci is a breathable windproof jacket without water resistance, designed for cool and dry conditions, with Castelli claiming an effective temperature range between 8oC and 15oC.Castellis piece includes a PFAS-free membrane and comes in short and long sleeved versions in sizes XS to 3XL for men and XS to XL for women. Its more expensive than Assoss jersey/jacket, costing 250 / $280 / 230 with sleeves.If you want more weatherproofing, Castelli also sells the Perfetto 3 RoS, which it says is around four times less breathable than the Do.di.ci and can handle a lower temperature range of 4oC to 14oC. It carries a 280 / $320 / 250 price tag.