Giordana makes their arm warmers from Super Roubaix fabric for loads of warmth. Use these in conjunction with a vest and a baselayer and you can ride in your favorite short sleeve jersey nearly year-round. Great from mid 40's to around 60 degrees. These arm warmers are built to last several seasons, and despite their reasonably low price, their quality and beauty are second to none. It's signature Giordana -- you'll look pro, you'll feel pro, but you won't spend Assos dollars.
These are very good arm warmers. Cozy interior, tight enough to stay put but not so tight as to bother you. I'm 5'9" with average (i.e., non-workout) arms, and the mediums fit just right. The seam is noticeable when you put them on, and may leave a mark after you take them off, but it didn't bother me when riding. In fact, I basically forgot I was wearing them, which is to me the hallmark of good gear.
I bought the small size for my always cold girlfriend and they fit her skinny arms well without sliding down. I've had the same pair of Giordana arm warmers (M) since purchased for cycling in 1996-ish and they are still working great with no elastic issues and soft on the inside. Great product for warmth augmentation and very stuffable. Highly recommended item.