This is possibly one of the most useful pieces of clothing I own in the UK's variable climate (OK, damp!). It's a light-weight windproof, showerproof shell from creators of most excellent kit - Rab. This is my favourite of the many wind-shells I have tried... it's performance pretty well matches the rather stunningly hi-tech name for what is essentially little more than a simple scrap of synthetic stuff... :o)

The Quantum in the title apparently refers to the variety of Pertex fabric used in the construction - incredibly lightweight yet highly windproof, water-resistant and breathable. The fabric has a very soft, silky drape - it's not stiff to wear or noisy in that crisp-packet kind of way that is often common to outdoors kit. The construction is pretty minimalist with detail limited to lycra-bound cuffs and half-zip that is the perfect length to pull on over a cycling helmet without snagging. I nearly mentioned my climbing helmet there as well but I wouldn't recommend this top for more abrasive activities such as rock climbing.

The light construction means it packs down incredibly small, about the size of a tangerine if you can be bothered to cram it into it's own stuff-sac (supplied). Personally I just screw it up and stuff it in a pocket, heck it's less bulky than a hanky after all...!

I love this top for cycling and running - the cut is very fitting so there's no flapping in the breeze. With a 38" chest I wear a size small, and in my case the Rab fits beautifully - close but not restrictive so if you're on the scrawny side of slim like many endurance athletes then this will be ideal. There are many other similar products around which I have tried but without exception the Rab fits better than all of them. It's great for early morning starts on the bike being easy to stuff away in a jersey pocket once things warm up, and being reasonably showerproof it's good enough to carry when the weather is changeable or mild but damp and drizzly.... which of course never happens in Cornwall....ahem! The best bit though..... mine is stealth black for that added bit of understated style (you can have a blue one as well...) - no horrible day-glos or nasty purple colours thanks. Visibility could be an issue at night I suppose but that's what third-party reflective stuff is for...

For more info check out http://www.rab.uk.com

Disclaimer: I would just like to point out that I have no financial or otherwise interest in Rab, rather I just like good kit. It may be a glowing review but then would you want to read about something is crap.... besides, stuff I don't like doesn't stick around long.... faux leopard-skin cycling tights anyone?