The Ride Aquazero Skull Cap is different from most in that it has a water-repellent band around the forehead to provide extra protection from the elements. That band is also wind-resistant.
The rest of the skull cap – the red stuff – is a Super Roubaix fabric so it provides loads of warmth. The black fabric is AcquaZero (there's a 'c' in there, although Ride don't use it), a material that used to be exclusive to Santini but no longer is.
At £54.99, you'd be forgiven for dismissing the Ride Aquazeros as just another set of standard bibtights but you couldn't be more wrong. These UK designed and Italian made tights are serious performers, and left me scratching my head as to why I'd want to spend any more on other options.