I use Nanoflex on damp days or when there is rain in the forecast. I think they have a little less stretch to them than the Thermoflex, but they are warmer and provide some nice protection from the wet. 6'-1160 and medium fits me well. They do stay in place nicely despite a little less flex. i may pull them up once or twice on a long rides if i make a stop, whereas the Thermoflex don't budge on me. Or i can just ride through and not worry about them. seem well made, only been through a few washes but no signs of any wear.
when you hear Castelli you default to size up. Thats not the case with the nano arm warmer. The medium conforms nicely although I do have thinner arms... true to fit. The material is thick without the heaviness. There is the elastic band material to keep it from slipping.
Nice thin material, well made arm warmer
These do the nanoflex thing really well and are sized reasonably well. I'm an extra-medium kinda guy, and the mediums fit pretty well. Like the nanoflex 2 leg warmers, these are a little long, but that's okay. It took me a bit of time to decide which was left vs. right and how the anatomical cut is supposed to go over the elbow-just remember that when you're on TV people should be able to read nanoflex or castelli.
Unfortunately the XS was too large for my thin arms. They did seem well made but runs large.
