It's tough to make arm warmers warmer. If we know we'll be riding in conditions where a pair of arm warmers won't keep us sufficiently warm, we tend to choose a thermal jacket. But, what if the day turns out to be intermittently cold and wet? Well, the Castelli Nanoflex Arm Warmers are designed for days that deliver everything from cold and wet to sunny and dry.
Nanoflex is a proprietary Castelli fabric. The mill begins with Castelli's super-warm and ultra-stretchy Thermoflex fabric, used in many of its winter pieces, and then coats the outside with tiny nanofilaments of silicone fiber. These fibers create a near waterproof barrier to moisture, and raindrops run off the fabric without soaking through. Despite its water-resistant finish, Nanoflex fabric remains highly breathable, keeping you comfortable in almost any conditions.
Silicone arm grippers keep the arm warmers in place on the hardest rides, and reflective logos are printed at the elbow and lower arm to increase your visibility to motorists in poor light conditions.
The Castelli Nanoflex Arm Warmers are available in four sizes from Small to X-Large and in the colors Black, Red, and White. Please note that Castelli recommends using these warmers at temperatures ranging between 50 and 60 degrees Fahrenheit.
I’ve had good luck with these warmers and they go a great job of keeping me warm on those shoulder season rides when I need a bit more. It’s probably just the Midwest in me, but I am not the type of person to wear arm warmers unless it’s less than 45 degrees. I typically will wear them between 35-45 and find them to work really well in that environment. For me personally, I would find them uncomfortably warm in anything about 50, but that’s just me. I am 5’11” 175lbs pretty slim arms and the Large fit well for me, they are a bit on the long side though. I haven't been able to try them out in any precipitation yet to comment on their wet weather performance.
I use Castelli arm warmers for my early morning rides where the temps are 60F or below. They're useful down to 50F w/o sun and perhaps 45F w/warming sunshine. I overlap the tops on the sleeves of my Gore WS short-sleeve base. It's a good combination between 50F and 60F. The arm warmers store well in a back pocket as the day warms into the mid-60s. I use the white model when riding pre-dawn for visibility. The black warmers absorb radiant heat during the day. The grippy tops stay up well thus far. I have 37" arms; the XL fits just right. I've used these for two, perhaps three years. An improvement would be to add reflective materials as is typical on Gore products.
Only thing i would say is that they are quite long....I bought a small and I have long arms for my height (6"2 wingspan and I am 5"9) so they fit just about right, but i could see someone with shorter arms having a problem with the length.
In terms of performance they are top notch, could not feel the wind at all.
Castelli really hit a home run with the Nanoflex fabric ? it's brushed for warmth, and repels wind and moderate moisture (rain, snow, etc.) with relative ease. No wonder why the Garmin guys insist on this stuff. Downside: zero articulation in the construction. No elbow bend or shaping makes the warmers bunch up where your arms bend. Not exactly uncomfortable, but not ideal either. Still a great product.