Anyone ever try Lizard Skins (http://lizardskins.com/products/?type=mountain&product_line=accessories) derailleur covers at sub -20c conditions?

They seem like a great idea, but I'm not sure they would remain flexible enough in cold weather)

I'm from Southern California. My idea of "cold" may be much different from yours!

Anyway, I have Lizard Skins on my bar ends. They are made of closed-cell Neoprene® covered with Lycra. I'm a scuba diver so I love Neoprene®!

The minimum service temperature for run-of-the-mill Neoprene® is around -60F.

I don't think you will have a problem

Eubi, he was talking about the plastic "Grunge Guards" that are now sold by Lizard Skins.
Im interested in them too, and ive found this thread.

http://www.bikeforums.net/showthread.php?t=54220&highlight=grunge+guards

seems good, but if you maintain your bike regularly, you dont really need it because they seem to pack with grunge (?) so i really dont understand the concept unless they absolutely seal the rear der from dirt. which also has to do with dirt on the chain. so it seems they will work better if you were to use a wax based lube like WL or boeshield, because it dosnt attract dirt. :D