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CastelliNano Flex+ Arm Warmer

Sale 26% Off$36.99 $49.95

Item # CST00EF

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Item # CST00EF

Dry wings.

A bright, brisk fall or spring day can turn drizzly in a flash and leave standard arm warmers damp, chilly, and certainly not doing their job to keep you warm. That is, unless you have a pair of Nano Flex+ Arm Warmers. Made from Castelli's proprietary, drizzle-blocking Nanoflex fabric, these warmers keep you comfy even when the weather goes south.

Nano Flex starts its life as Castelli's super-warm and ultra-stretchy Thermoflex fabric, used in many of its winter pieces, and then gains and outer coating of 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, Nano Flex fabric remains highly breathable, keeping you comfortable in almost any conditions.

Across the back, Castelli utilizes a panel of its lighter Nano Light fabric to increase stretchiness around your elbow for full freedom of motion and comfort no matter how many miles are on the schedule.

  • Water-resistant warmth for your arms
  • Soft, brushed lining protects against the chill
  • Silicone grip holds hems in place
Tech SpecsSize
Tech Specs
[front] Nano Flex, [rear] Nano Light, DWR treatment
Recommended Use
Manufacturer Warranty
1 year


Arm & Knee Warmers





Rider Weight

99.2 - 132.3lb

(45 - 60kg)

99.2 - 132.3lb

(45 - 60kg)

132.3 - 154.3lb

(60 - 70kg)

154.3 - 176.4lb

(70 - 80kg)



Short/Jersey Size XS - S S - M S - M L - XL 2XL - 3XL
Short/Jersey Size:
Take your typical cycling short or bib sizing for comparison.

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Poor Customer Service

    For two weeks I've been trying to resolve a simple warranty issue. I bought Castelli arm warmers and within the year warranty period they ripped at the silicone gripper. I sent photos to Backcountry. They would only replace if I cut them up. I was attempting to wear them as they are the only pair I have. I offered to cut them up once the replacements arrived. They wanted no part of that. The arm warmers are defective whether or not I cut them up. To insist on cutting them up before they will ship new ones is taking advantage of me and my ability to continue to ride my bike. Very poor customer service.

    Castelli Arm Warmers Rip

      After 6-7 wears and 2 washings the arm warmer ripped at the silicone gripper when I was putting them on. Arm warmers should definitely be more durable than that. It appears they were not sewn well.

      Perfect fit

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

      Another great product from Castelli. The right length, warmth and protection as needed. Purchased size medium.


      • Fit: Runs small
      • Size Bought: L

      I have the old nannoflex arms, I used it for 4 years, I am a RAPHA customer 99% of my kits, however, Castelli Gabba and this nannoflex are the BEST in the market

      Thank you for the review!!!

      Awesome arm warmers for cold weather

      • Familiarity: I've used it several times

      I’ve had several arm warmers, and these are excellent. I don’t feel any wind coming through and they stay up well on my arms. They’re also long enough that I don’t get a gap above or below them.

      Warmer Warmers

      • Familiarity: I've put it through the wringer
      • Fit: True to size

      Arm and Leg warmers are great, you can peel them off mid ride and they don't take up a ton of space. Castelli's warmers are on the warmer side of the warmers I have owned in the past, and a huge benefit is they will shed water too. Not water proof, but they hold their own just fine, these have been my go-to option for cool morning rides I love them, and the fit and quality is solid.

      best. arm. warmers. ever.

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

      Review title says it all but I'll elaborate. Superior water-proofing yet breathable. I pair these with the Gabba and can take on any weather conditions. Normally I size up with Castelli clothing but I wanted these to fit tight so went with the recommended size per the sizing chart. They fit like a second skin. Sadly, I only wore these a few times and crashed tearing a hole in one warmer :(

      Boom Shaka

        Best arm warmers that I have worn. articulated right, fits well, dialed in. If you need arm warmers, get these ones.

        The best warmers ever.

        • Familiarity: I've put it through the wringer
        • Fit: True to size
        • Size Bought: L

        I dunno what to say. It's water repellent, it's warm, it dries fast, and it fits amazingly well. I rode straight through heavy rains with this, and for the first few hours, rain just bounces off. Water eventually got through, and yet I stayed warm the entire ride. Kinda like a wetsuit, actually.

        The thing with water repellency is that, even though you'll still end up getting wet, it still shrugs off a lot of rain as water eventually gets in. A lot of COLD rain.

        Their sizing chart makes no damn sense; I went to Wiggle and checked Sportful's warmer size chart (they're both sister companies). The material's super stretchy and comfy, so I didn't size up like most Castelli pieces.

        My only gripe is that the Castelli lettering isn't reflective, which would be a nice safety feature during darker days. It's white rubber text glued on which I hope doesn't peel off down the road.

        MJ....Like all other cycling kit, turn them inside out when you wash them (in cold water, of course) to prolong the lettering. Time will unfortunately take it's toll though as it will with most things...remember Bilbo's riddle....or was it Frodo?