Benjamin A.wrote a review of Mavic Ksyrium Merino Arm Warmer on January 30, 2018
Familiarity: I've put it through the wringer
I'm not a fan of lycra or felt-lined arm warmers as lycra does nothing to block the wind and felt-lined always becomes too hot. These are a great middle ground: they take the edge off the cool days but are good when the temperatures rise into the 60s.
The only fault is that they are just not long enough and will inevitably end up poking out of your sleeves. Longer "euro-style" sleeves help a great deal, but even with the longer sleeves these arm warmers will occasionally peak out.
They are now my go-to for rides that will end up mostly in the sun or north of 50 degrees, but only when I am wearing euro-length sleeved jerseys.