Nanoflex really is at the cutting edge of fabric technology. We go into the science in more detail below, but the result is that it actively repels water. Nanoflex Pro is for extreme conditions and is the answer when you're wondering what to wear for long rides in the rain Just like Castelli's Thermoflex fabric, Nanoflex is warm and breathable. It's extremely soft to the touch and traps a layer of warm air next to your skin. Its secret, however, is that it's coated with millions of microscopic nanofilaments. This nanotechnology treatment causes water to simply bead and run off. Nanoflex Pro uses an extra layer over the thighs, knees and seat area to further increase protection from wind and rain. Nanoflex Pro tights aren't 100% waterproof, nor does Castelli claim that they are. They will, however, keep you drier for longer than virtually any other bibs out there To ensure complete comfort on long rides, the Nanoflex Pro features Castelli's Progetto X2 Air seatpad. The Progetto X2 is produced using 3 layers, each of which has a very specific purpose. To provide comfort where it's needed most, there is perforated viscous padding at any high pressure areas. Multi-density foam is used to provide variable thickness - padding where it's needed and less where it isn't, to maximise your freedom of movement on and off the bike. Finally, a four way stretch, antibacterial layer allows air to flow into the surface fabric to aid evaporation. Castelli calls this "the most comfortable seat pad on the planet" and we don't disagree!The Sorpasso tight features an ankle zip, which allows a snug, yet comfortable fit. This snug fit keeps cold air out and allows the Nanoflex fibres to trap warm air next to your skin Unique to the Nanoflex Pro is a large, reflective band on the lower leg. When getting those extra training miles in means venturing out in the dark, this band will help keep you safe by making you more visible to other road users. In addition, it further protects your legs from wheel spray The Nanoflex Pro is an exceptional garment that will see you well prepared for all those long winter rides Features: Nanoflex fabric provides outstanding warmth and stretch, with water resistance Minimal seams for maximum water resistance State-of-the-art Progetto X2 seat pad for complete comfort on long rides Seamless bib straps sit flush against the body, for exceptional comfort Large, reflective band on lower leg makes you more visible to other road users and provides further protection from spray Ankle zip provides a snug, secure fit Temperature range: 6-18°C Fabric: 86% Polyamide (Nylon), 14% Elastane (Spandex) Weight: 323g (size S)With roots dating back to 1876, Castelli has been at the forefront of fabric technology for almost 40 years. Alfredo Binda, Gino Bartali, Fausto Coppi, Jacques Anquetil and Louison Bobet were but a few of the legendary athletes clothed by Castelli. More recently, Bernard Hinault wore the first windproof jersey when he won Fleche Wallone. Castelli made that too! Buy Castelli Clothing from Chain Reaction Cycles, the World's Largest Online Bike Store.