Castelli Nanoflex Leg Warmers

Warm and dry never looked so good.

If there's one failing to most legwarmers, it's that they absorb water like a proverbial sponge. On rainy days, they end up waterlogged and providing compromised warmth. However, the Castelli Nanoflex Leg Warmers are perfect for riding in conditions that are both cold and wet. Then again, outside of Mojave heat levels, we can't think of any condition that won't benefit from Nanoflex.

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) receiving an exterior coating of ultra-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 condition.

Silicone leg grippers keep the Nanoflex legwarmers in place on the hardest of rides, and ankle zips make them easy to get past the largest feet. And lastly, reflective logos are printed at the knee and below the calf in order to increase your visibility to motorists in low-light conditions.

The Castelli Nanoflex Leg Warmers are available in four sizes from Small to X-Large and in the colors Black, Red, and White.

  • Reviews
  • Q & A

Looks Average!

  • Fit: True to size

I have not tried it yet but the denim looks below Castelli standard.

These leggings are dope

  • Fit: Runs small
  • Size Bought: Small

I bought these for a few reasons--they are bright, they were on sale, and they are water resistant. I've used them on a rainy day, light rain w road splash. They were great! Kept my legs dry and warm. It was high 50's degree Fahrenheit.
I found the fit to be snug but I liked it. No baggie leggings for this girl. I'm 5'8" and weigh 130lbs and the smalls were clutch.
I love the bright red color. I read an article that did a study on some of the best things to do to stay safe riding on the road--to be seen by cars. And bright leggings was one of the top ways to be seen. So I'm a fan.

Perfect to pair with the bib shorts

  • Familiarity: I've used it several times
  • Fit: Runs small
  • Size Bought: large

These have the same rain shedding ability of the Nanoflex bib shorts, and the material seems to be more windproof than typical warmers as well. They are not rainproof, but water will bead up and you will stay dry and comfy much longer than with typical materials. And they breathe well so you can ride in comfort.

They do run small: I ordered size large, the same as my other Castelli leg warmers, versus medium in most things. They are not as stretchy as normal warmers (and take some care to put them on), and I don't think I could have worn medium. Especially at the ankle, I could not go any smaller. But the result is a perfect fit, but with little margin for error.

Nanoflex material really is fantastic, and paired with the Perfetto jersey and neoprene gloves in wet weather I find I can ride farther and with much more comfort than in normal materials. They do get wet eventually, but continue to regulate your temperature and remain much more comfortable than normal gear.

I wanted to love these, but...

  • Familiarity: I returned this product before using it

I truly was excited to try these leg warmers. I unwrapped them and the material (in and out) seemed very nice (fleece on the inside) and as if it would do the job to keep my legs warm and protect me from the elements (rain, wind, cold). However, as I put one leg into the warmer and rolled it up my leg, I noticed the material was separating from the "thigh gripper" material in several places. Unfortunately, I will not be able to try out these legs warmers because they are falling apart right out of the package, so back they go.

The marketing is true

  • Familiarity: I've put it through the wringer
  • Fit: Runs small
  • Size Bought: Medium

If you read the marketing description, you will get a good feel for how these work. I found them to be good at shedding light rain. These are not anything like rain pants, but on the other hand, rain pants don't breathe well. These definitely run small -- all my other legwarmers are sized small, but I fit comfortably into sized mediums in this case. I didn't order the small size, but given how tight the ankles are on the medium size, I think I would have had to exchange them if I had.

job done.

  • Familiarity: I've used it several times
  • Fit: Runs small

I have these along with the arm warmers and they have done the job this fall in slc. I have a long slender build so both the arm and leg warmers fit me very well , though most people are tending to size up.

So what size do you wear?

Great Warmers,

  • Familiarity: I've used it several times
  • Fit: True to size
  • Size Bought: XL

They run tight like all Castelli, but I've worn these for 3+ hours without any discomfort. Right out of the bag you can tell these are a different class of material and they feel much more like the Gabba exterior than your typical warmers. The bags they come in are classy as well and can be used as a wallet for storing CO2, Levers, money, etc. Nice touch for the price you are paying.

They do not disappoint. On a typical 3 hour ride here in Northern California, the leg warmers perform excellently in temperatures ranging from a low of 30F to a high of 55F. They are quick to dry after the ride as well.

I do wish that the ankle zippers were "locking zipper" but it works just fine when tucked into my overshoes. But even without overshoes I didn't really notice anything once I got going.

Zipper Digs into Your Ankle

  • Fit: True to size

Have used the leg warmers a half dozen times. One of the times the zipper continually would dig into my ankle. Hey I bought the red ones anyway. What's a little blood.

I guess I had different expectations at this price point.

Otherwise they worked as expected. Warm and sheds water well.

Size up!

  • Familiarity: I returned this product before using it
  • Fit: Runs small
  • Size Bought: small

Boy they weren't kidding on the running small part. Since an XS Pearl Izumi women's leg warmer is still too big for my little chicken legs, I figured a small in unisex Castelli would fit. Nope, returning for a medium.

Tore up after one wear

  • Familiarity: I've used it once or twice and have initial impressions

I wore it only once and after one wear. Even worse is apparently since I bought it a bit early (in September) I am ineligible for an exchange or refund.

One leg warmer to rule them all

  • Familiarity: I've put it through the wringer

I have had nothing but great experiences with this leg warmer.

First the fit, is great. I am 6'1" about 160 pounds and I chose a medium. I had some slight bunching up on the back of the knee but no discomfort like others have had. The bottom zipper also did not create any irritation by the ankle which I have seen in some leg warmers. Warm enough to keep me warm in ~3 degree celsius temps and cool enough in 20 degree celsius. Overall excellent leg warmer and highly recommended, if you have an issue it is probably due to improper sizing.

Like sandpaper

  • Familiarity: I've used it several times

The fleeced interior on these is like sandpaper. Too rough to wear on even a few warm-up laps at a cyclocross race.

not great for actual movement

  • Familiarity: I've used it several times

I was disappointed in these, I usually have enjoyed Castelli's clothing a lot. They seemed like they fit great when I firt put them on but when pedaling (bending your knee's) it bunched on the back and rubbed. I see that a lot of other reviewers had similar circumstances. I would suggest another brand of leg warmers, I have some craft that work better.

I just wanted to add that my problem is with the seam, and the rubbing it generates on the back of the knee. I consistently get enough rubbing from that seam on the back of my knee that it rubs the area raw and eventually scabs. I really like these warmers, however I wish Castelli would do something about minimizing or reworking that seam.

Cyclocross Must Have

  • Familiarity: I've put it through the wringer
  • Fit: Runs small

These things are great for cyclocross.

They repel water really well and are nice and warm. Tight fitting as most Castelli gear is, but also very stylish!

Works well but watch sizing.

  • Familiarity: I've put it through the wringer
  • Fit: Runs small

I have used these in an extended rain ride. The water beads off like it is supposed to. The nanoflex stuff does not stretch like normal warmers do. I ordered a size L, but really need an XL. Like another reviewer here, the seam rubbed the back of my knee raw. In this case the seam was not in the middle of my leg, while the warmer on the other leg was and did not experience rubbing. The seam needs to be exactly in the middle to avoid the rubbing. At least with my legs.

Feels Like Cardboard

  • Familiarity: I've used it once or twice and have initial impressions
  • Fit: Runs small

I'm not sure what Castelli had in mind with these, but they felt like I was wearing cardboard. At the end of a 50 mile ride, the skin at the back of my knees was rubbed raw.

How does one decide between the Nanoflex...

How does one decide between the Nanoflex and Thermoflex leg warmers, other than price? In other words, why would you choose one style versus the other? Thanks.

Best Answer

Confucius say - go with the Thermoflex :) Almost the same :)

The nanoflex is very water resistant, so I'd pick the nanoflex if the weather is iffy. For cold and dry, pick the thermoflex.

The only way to go

  • Familiarity: I've put it through the wringer

The nonflex are the only way to go. Great item, and allows you to reduce the amount of winter wear, without feeling the effects of the cold

Runs small

  • Familiarity: I returned this product before using it
  • Fit: Runs small

I ordered a small, like all other legwarmers ever. I am a female and usually wear small shorts and leggings. I couldn't get these over my calves as a small, so I am returning them. I can't speak to the quality, but they seem nice like all other Castelli stuff.


  • Familiarity: I've used it several times

Just put these back on after a hot summer and noticed that the material around the knees was flaking off. Not sure this is designed to happen after one season.