Castelli Nanoflex Arm and Leg Warmers


Castelli’s Nanoflex Leg Warmers are well designed and comfortable with the added bonus of being water repellent.

We’ve reviewed Nanoflex kneewarmers and armwarmers on in the past and we’ve been impressed.

The big selling point here is the water repellency of the Nanoflex. Castelli use their Thermoflex (a brush-backed Roubaix) fabric with the addition of “tiny silicone nanofilaments on the surface”. This results in water beading up and rolling off.

Castelli don’t claim that Nanoflex is completely waterproof. It’ll keep road spray and showers out but harder rain does work through, especially through the bit at the front of your knee that you stretch repeatedly as you pedal. But the point is, these feel like any other leg warmers in terms of feel and breathability – like most, they’re made from nylon and Lycra – so there’s no down side to that extra water repellency.

How long does the Nanoflex keep doing its job? Well, I did a little test and found that the knee warmers I have from a couple of years ago that have been through the washing machine a zillion times weren’t doing much in the way of keeping water out any more. Arm warmers from about a year ago that have been through the wash a couple of dozen times were still doing well.

I contacted Castelli’s UK distributor, Saddleback, to find out if that was to be expected and they said: “Light ironing over the surface will rejuvenate the protection.”

That’s what I did and – hey presto! – it worked. I wouldn’t say that the performance is right back to original levels, but it’s not far off.

Nanoflex aside, these are good leg warmers in their own right, coming with just one flatlock stitched seam up the back, which I haven’t found at all irritating. The elasticated gripper has silicone on the inside to hold it against your leg, and on the outside to keep it in place against your shorts. I’ve never had any trouble there. A YKK zip at the back makes getting them on and off easy, even over your shoes.

Castelli give a temperature range for every item of their clothing and we usually agree with them. In this case, they say 8-16°C. You could wear these when it’s a little colder than that, but chances are that if it’s that nippy there’s no chance you’ll want to remove your leg warmers mid-ride, so you might as well go for tights.


Warm, comfortable leg warmers with the added bonus of being water repellent.



Castelli Nano Flex arm warmer


Starting with a standard pair of their Thermoflex armwarmers and coating it with millions of silicone ‘nanofilaments’, Castelli have created a water repellent fabric called Nanoflex that causes raindrops to bead off of the fabric as you are riding keeping you drier for longer. That’s the theory; and the practice?

Well, in practice the Nanoflex arm warmers, like the Nanoflex knee warmers we tested recently, are pretty impressive too. Light rain and road spray are just blown off the material by the wind as you travel along. This process works in heavier downpours until the fabric gets overwhelmed and once wet the thermal fleece fabric keeps you warm so it’s no real problem. In the dry they work exactly the same as the standard Thermoflex warmers they are based on. While warm they are not overly so and can be worn on spring/autumn mornings without the fear of overheating.

The Thermoflex material offers thermal protection using a fleece inside which also provides comfort as well. The fit is close with the size tested covering from wrist to armpit on me, there are no size guides on Castelli’s website but to give a little idea of how they measure up my arm length is 46cm and a 18cm diameter bicep. They stayed put all ride thanks to silicone grippers either end and the fact they are so long stops that annoying gap between armwarmer and jersey sleeve happening.

Price wise we’re looking mid to high end here at just over the thirty quid mark and being just a couple of pounds extra than the standard Thermoflex the Nanoflex coating is a worthwhile extra. The de rigueur colour choice of white, black or red is available in sizes from small to extra large.

All in all the water resistant coating makes good sense especially at this time of year when a full waterproof jacket is too warm in the rain but paired with a gilet these warmers keep the worst of the dampness at bay. Thin enough to be used as a layer in the minus temperatures winter throws at us under a softshell or jacket coupled with being able to use them in spring/autumn without overheating makes them versatile and probably one of the most used bits of kit in your wardrobe.

There is a downside though as ever, a large seam runs the full length which can get irritating after a while plus the graphics don’t look like they will stay attached very long and look a bit rubbish once the material is stretched over your arm.


A veratile product that should be of use for at least 75% of the year in the UK. The water repellent coating is impressive and works in all but the heaviest rainfall but by this stage you’ll probably be thinking about a waterproof jacket anyway. A good fit though with a reasonable price tag