Based on their successful Sanremo Speedsuit, Castelli's latest product is a one-piece winter package

Based on the Sanremo Speedsuit that was ridden to success in Paris-Roubaix by Johan Vansummeren last year, the brand new Sanremo Thermosuit from Castelli is their latest answer to riding in cold weather.

They boldly claim the revolutionary design allows you to wear just a baselayer and the Thermosuit for riding in the winter. How come? Its unique design forms an airtight seal around the body which delivers full protection from the elements and should, claim Castelli, gives better regulation of body temperature.

A downside of a sealed airtight approach is potential heat build-up so to overcome this Castelli and used a combination of materials in key places to give a good balance of warmth and breathability. The front uses Gore's Windstopper X-Lite Plus fabric which is well known for its windproof, breathable and water-resistant properties.

Around the back, and for the tights, is a Thermoflex Core Due fabric. Its hollow-core polyester fiber design means it can trap air providing a warm layer around the body. It's lighter than other fabrics too so places less restriction on the legs during pedalling.

Inside is their Progetto X2 Air chamois. An object of high technology with a seamless bacteriostatic (an anti-bacterial finish) fabric that conforms to the shape of the body with a multi-density foam with variable thicknesses to deliver comfort in the key areas.

You get three pockets around the back and a full-length ykk camlock zipper. There's reflective details and, as the photos show, it is bang on trend with the fluoro yellow left arm and stripe down the leg.

The Speedsuit's biggest claim was the aerodynamic advantage it offered over separate shorts and jersey outfits, and there's no reason why you can't have the same aero benefits through the winter months. Castelli say the new Thermosuit provides the weight and aerodynamics of a summer clothing but with the protection of winter garments.

The Castelli Sanremo Thermosuit is available in six sizes, from small to XXX-large, in black/yellow fluorescent.  And it costs, are you sitting down, £250. So not cheap, then. But innovation doesn't come cheap, does it. Check out http://castelli-cycling.com for more info.

If you're need further explanation, have a watch of this video:

David has worked on the road.cc tech team since July 2012. Previously he was editor of Bikemagic.com and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds.