Castelli Thermoflex arm warmers – review

Arm warmers play an important part in bridging the weather gap between a ride that only needs jersey and shorts, and a ride that requires full cover. These Thermoflex arm warmers from Castelli perform their relatively simple job superbly, providing plenty of warmth for changeable conditions and have an excellent fit with top-notch grippers.

I love arm warmers and consider them a vital piece of kit to have in my arsenal, perfect for any ride where it starts off a bit cold but is expected to warm up later, or if there’s a bit of a nip in the air that doesn’t justify exposing bare skin. The advantage they have over, say, a long-sleeved jersey is that they’re really easy to remove mid-ride and store in your pockets. So easy, in fact, that you don’t even really need to stop to get them off. Think about those mid-summer sportives that start at 7-8 in the morning. You know that it’s going to be warming up to 20 odd degrees later, but don’t want to catch a chill before that happens – well, arm warmers are the answer.

Castelli make two main kinds of arm warmers: Nanoflex and Thermoflex. Nanoflex is their water resistant material, designed to both retain body heat and keep the water out. That dual function puts them slightly higher up the range at £30 than the £25 Thermoflex warmers we have here, which are designed purely to keep your arms toasty.

As cycling clothing goes, arm warmers are one of the items that tend to not be packed too full of features, and that’s the same with these. The outer material is smooth to the touch and reasonably supple, while the inside is lined with a fleecy Roubaix-style fabric designed to trap heat next to the skin. Castelli claim a temperature range of between 5-15 degrees for these and I’d say that’s about spot on, but they do a good job stopping the wind, too, so have a place on warmer but windy days, and breathability is also good. That gives the Thermoflex arm warmers a wide temperature range and so they offer plenty of versatility.

One of the main issues with warmers is slippage. As they’re essentially just two tubes of material that fit over the arms, they need to be anchored in place otherwise you’ll quickly just have a collection of fabric resting around your wrists, and no-one likes baggy arm warmers. At the upper end of the Thermoflex warmers, Castelli have a silicone band which works a treat. I’ve ridden in these extensively – spring being the exact time of year when a set of arm warmers are needed more often than not – and they’ve stayed in place superbly on every single ride. Obviously the other key factor here is sizing: if they’re baggy they’re likely to slip no matter how good the grippers are, so make sure to check. Castelli offer four sizes: S, M, L and XL.

The smart thing about the grippers is that those clever people at Castelli have put a layer of them on the outside as well as the inside at the top. While the outside band holds them up, the inside band is there to hold your sleeves in place. It’s another smart little feature that works very well, and plenty of other brands could take notice as it’s surprising just how irritating your sleeves riding up can be. Although, again, nothing makes this easier than clothing that fits correctly in the first place.

At the wrist, a simple elastic cuff does the job and does it very well indeed. And the right arm has a coloured band that comes in a variety of colours including red, yellow and the blue shown here. If you’re feeling particularly Euro, or your wardrobe demands, you can also get them with the main colour as white instead of black.


Castelli’s Thermoflex arm warmers may well be the best arm warmers I’ve ever used. They’re comfortable, don’t move at all when you’re riding and strike a good balance between being warm and being breathable. I’ve used these arm warmers in a wide variety of conditions and the amount of use you’ll get out of them more than justifies the £25 price tag.


– excellent fit
– grippers hold them up well, and the extra gripper for jersey sleeve is a smart touch
– Good choice of colours when most come in black or black


– Nothing, to be honest

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