The Hydrolite is a radical new jacket that pretty much does away with any conventional jacket fabric, leaving just the waterproof membrane. It works differently to most jackets in that rain penetrates into the membrane, but, crucially, it doesn't get through to the other side. Meanwhile, heat helps to push any sweat vapour out quickly so you stay dry inside. This translucent top really delivers outstanding performance once you're used to its rubbery feel. It's also light (186g) and packs up small.
Unfortunately it's too delicate for real mountain bike work. We tore one sleeve to shreds while it was tucked in the back of a CamelBak... Then another not even particularly pointy bush tore a string of holes in the other sleeve.