As far as armwarmers go, these are fine. They are, however, sized for midgets with arms like a T-Rex; vestigial, in other words. While I am tall and muscular, I do not actually haves biceps, both having torn due to heavy exertion in bygone days. So my upper arms are of modest size. Still, these puppies are tight. Really strong elastic. I have similar arm warmers from Exte-Ondo that are high quality and fit well. The lightweight versions they sell are fine. These, not so much.
These are a good compromise between thermal arm warmers and lightweight warmers. Have ridden in 40-50 degree temps while soaking wet and they kept me warm. Also ridden in 60 deg temps and not uncomfortable. Ordered size medium and 157 lbs., 5-9, fit is snug but they don't fall down.
I have several other armwarmers so I'll compare this one to them. I have a few Pearl Izumi in size Medium, but I ordered size Large in Castelli and that was the right choice. It fits pretty snug but not uncomfortable for a few hours. I'm really not sure if it's warmer or not, but I think it looks a little better. It's a keeper :)
Got this simply because I didn't want to wear cycling winter jacket and over heat, come home drenched in sweat. Days that dips passed 30 degrees I wear these and thermal L/S base layer fleeced thermal jersey and wind vest and I'm good.
I guess I've got big guns because no arm warmers fit anything but tight
These are good once you get them in place
Live in FLA, ride early, during winter these warmers are perfect
