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Castelli Thermoflex Arm Warmer
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Item # CST00GM

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  • Black, S ($29.96)
  • Black, M ($29.96)
  • Black, L ($29.96)
  • Black, XL ($29.96)
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Item # CST00GM


No more goosebumps.

Cold arms are uncomfortable and distracting when you're pushing through a cool shoulder-season ride, but it's an easy problem to fix. Slide on the Castelli Thermoflex Arm Warmer before you head out on a crisp day, and the microfleece-lined thermal fabric will hold heat next to your arms while remaining breathable if you break a sweat. Features like a comfortable cross-wrap at the wrist and silicone gripper promise to keep fit issues at bay so you can put each warmer on and go ride free of distraction.

  • Insulate your arms on chilly days with this plush warmer
  • Thermoflex fleece holds heat close but remains breathable
  • Silicone gripper prevents slippage and drooping
  • Cross-wrap cuff creates a comfortable fit at your wrists

Tech Specs

Thermoflex fleece
Claimed Weight:
[pair] 67g
Recommended Use:
Manufacturer Warranty:
1 year

Size Chart


Arm & Knee Warmers
Rider Weight

99.2 - 132.3lb

(45 - 60kg)

132.3 - 154.3lb

(60 - 70kg)

154.3 - 176.4lb

(70 - 80kg)



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

Reviews & Community


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Love it

  • Familiarity: I've put it through the wringer

Very comfortable. Ive been commuting for the past year and they have taken a pounding and they still get the job done.

Runs very small

  • Fit: Runs small
  • Size Bought: XL

I am 6'0" 190 lbs with average size arms. I first ordered the L and could barely get it on. It was even tight on my wife, who weighs 125 lbs. I then tried the XL which was still tight on me. I'd think Castelli could give biceps size in their sizing chart, everything else is a waste of time. If you order anything from Castelli, from my experience with their products, order up at least TWO sizes from your usual size, and keep your fingers crossed.

Next Generation

  • Familiarity: I've used it several times

Upgraded to these as my go to road arm warmers and fulfilled my Castelli expectations. Thermoflex is super soft and flexible while moving with you during rides, etc. The new cross cut cuff offers a nice smooth and unrestricted closure. As opposed to the Nano Flex version, these are much more elastic and conform to your arms much closer. This can be attributed to the lack of the water-resistance treatment that the Nano Flex versions receive. Fit is Castelli- race fit as expected. My arms are somewhat long without bulk and I opted for medium for a 6'2" rider.

Hi, can you tell me what you mean by "cross cut" cuff? They talk about this in the specs too and I don't know what that means and can't tell from the photo. Is there some sort of strap on the bottoms, or are these just normal arm warmers? Also, are these heavy fleece lined, or light? Thanks!

Very nice - but not for big guns

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

I have the Thermoflex knee warmers and got these to match. I haven't ridden them in temps below 50 degrees yet, but they seem plenty warm and are comfortable. No falling down at all. I've got long skinny arms, and they're pretty snug and long. I pull them up to my armpits and still go down over my wrists. It works for me, but caution if you've got big or thick arms.

Avg. ride time: 4h 53m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

They do the trick!

  • Familiarity: I've used it once or twice and have initial impressions
  • Fit: True to size

These are a good value and definitely do the trick. Temps dropped today and the arm warmers worked great. These are well made and have a good weight fabric. Inside the sleeves is a nice soft low fleece type backing; comfy. More insulating than your typical lightweight SPF type warmers. I bought a size Medium and they fit well.

Avg. ride time: 14h 14m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

Castelli Arm Warmers

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

It works for me. Very warm! The only cons is that the strap is a little tight and I have thiny arm, but it is bearable.

Hi, I'm 5'8, 145 lbs and was going to get a size small. The medium works for you?

AM - unless you have skinny arms, consider the L. Especially if you ever put the arm warmer over even a thin base layer. The
L is even tight on my wife who weighs 125 lbs.