Mennon Gray Cards

Pros: -Card maintains its constant gray appearance
-It's ideal for studio work
-It helps you to get the right whitebalance/colortemperature and exposure
-Price is ok, not derision-cheap, but undoubtedly not too expensive, as graycards aren't really cheap
-You receive two seizes, so you can use one at home, and you can put the small one in your camera bag
-It's made of thick cardboard, that's painted with neutral gray.

Cons: -Don't put your sticky fingers on it, as you will see marks pretty easy
-It's not waterproof, so don't use is outside while it's raining

Other: It's a good buy, but you have to know how to use it.

Pros: Grey cards with good price. Decent packaging.

Cons: Instructions come only on CD. There should be a printed version. Well, I don´t miss it since I know how to use this. But for begineer photographers this could be a drawback.

Other: If you are a hobbist photographer, buy this. I don´t know, however, if these gray cards are good enough for professional photography. But for the price, what can I say?

Pros: Comes with two sizes of 18% grey card, and a CD with lots of help and advice.

Cons: None. They're simple and they come with minimal instruction.

Other: If you're an experienced photographer you'll probably know the uses of grey cards so I won't bore you with a few details. :)

Pros: Comes in two sizes.
Grey sheets mounted on card stock seems durable enough.

Cons: It's made of paper, so be careful how your treat it.
Not nearly as cheap as I would like, but cheaper than the alternative.

Other: Pretty decent cards for the money.