With a winter jacket that carries a sizable spec list it may be challenging to understand the complexities and nuanced engineering that Assos pursued when creating the Equipe RS Winter Jacket. So let's start with its purpose. Assos designs the RS for the year-round cyclist -- one who enjoys the wintry alpine summits with 12-foot high roadside snow-banks just as much as the coastal hauls in peak summer. Created from Assos' Project johDah line of SPHERE fabrics the RS is a winter layer for heavy-exertion riding and woven using lightweight and heavyweight layers together in an astounding form of selective precision to protect the rider not only from the winter elements but also from exertional body-heat and sweat.The front of the RS uses Assos' SPHERE Light fabric which acts as a mid-weight wind and water barrier that also allows for breathing. Inside that layer is the Tibet fabric for lightweight insulation that also pulls sweat from the chest and abdomen for evaporation. The upper back and forearms receive SPHERE Medium -- Assos' thickest material -- for maximum insulation and breathability while also remaining windproof and bonded with a water-repellent layer for mid-ride shower protection. Rhombus fabric boosts the SPHERE Medium's insulation on the back and forearms where riders need it most. The remaining zones are protected by warp-knitting layers of ZigZaggy Foam and OSMOS Heavy fleece which afford the RS with a high degree of stretch.There features are not quite evident to the naked eye however a unique and heavily-prominent feature is the mid-back level pocket which Assos calls the Thermobooster Pod. Designed for days when the climate is extra humid or more demanding the pocket houses Assos' Alleycat Clima Capsule or Thermobooster Lid -- also known as the Equipe RS Clima Capsule and Equipe RS Winter LS Mid Layer respectively and sold separately. So you'll be able to carry the descent barrier or insulated hoody (or both) depending on your ride plans.