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I'm after some thinnish arm warmers, about the thickness of a regular jersey. Just to take the edge off the early morning commutes. Would rather not spend too much. These look good, but the sizing looks a tad small even in large.
http://www.on-one.co.uk/i/q/CLPXCOLAW/planet-x-coolmax-seamless-arm-warmers
I've got a set of the On-Ones that you linked to, they are fine. They aren't a close weave material, think more along the lines of a surgical sock than something windproof. Can't remember what size I got. They are light enough in colour to act as sun protection as well.
Endura merino ones are good.
Don't buy black ones. If you do, after a few weeks you will only be able to keep one arm warm at a time.
I bought some cheap (£8) white ones from Amazon for a recent SDW ride, they were fine. Basically a Lycra sleeve with grippers at the top.
Morvelo ones for me.
Some old Planet X ones which have been awesome. Fit my pencil arms a treat.
@mcnultycop - Morvelo ones look good, what's the sizing like?
Another vote for the morvelo thin ones (screens?)
I take XL which matches my jerseys and most other kit (except Italian sized in which case I'm xxl)
Mrs Rider invented me some arm-warmers back in 2002, and they are still in use today (winter-time, not literally today)
Take some women's hold-up/over-knee socks and cut the feet out. Slide on to arms. Robert is your mother's male sibling. Plain colours or loud, lr whatever is knocking about. 
Don’t buy black ones. If you do, after a few weeks you will only be able to keep one arm warm at a time.
??
I've had various pairs of roubaix style ones over the years but by far the best I've owned, and the only ones that get used now, are Defeet Armwarmers. Both the non-merino and merino are great - stay up without silicone grippers and just more comfortable.
Black makes sense for armwarmers - increases the solar gain when it's cold but the sun is shining.
I have some barely used assos ones which are XL but too tight for my arms, I'd say they're more a large. If you drop me a mail and give me a few quid for postage then you can have them if you want.
I’m XL in the Morvelo. I lift weights though so I’ve got reasonable sized arms. They sized up as expected.