I have these and love them. The liquid elastic at the top is nice and has a much better feel than my previous leg warmers. Whether it holds or not over time is another story. But nothing is worse than a warmer with shot elastic.
Living in SoCal I can't say how low these rate down to for temperature. However, I did recently wear these during a morning ride in sub-40F temperatures and I never felt even the slightest bit cold or even cool. So they're good down to at least 35-40F.
Sizing information is impossible to find for this product. Ask any shop. They don't have it. However, Giordana was nice enough to pass the information along.
Hopefully this will help you make your purchase decision. I definitely don't regret mine.
Size - Length - Circ. at top - Circ. at Wrist
S 605 mm 390 mm 190 mm
M 620 mm 400 mm 200 mm
L 640 mm 410 mm 210 mm
XL 660 mm 420 mm 220 mm
S 23.80in 15.33in 7.50in
M 24.50in 15.75in 7.87in
L 25.25in 16.25in 8.25in
XL 26.00in 16.50in 8.66in