Best 3 tone grey card to get for 7D?

[matt9b]

Hey guys, I got my 7D recently, and I want to improve my white balance and skin tones, so I'm looking to get a professional 3 tone grey card. All of the cards here in the UK seem to look different. E.g. 'neutral' grey on one card is a completely different shade to 'neutral' grey on another card. Some are darker, some a lot lighter. Yet they all claim to be neutral grey. It makes me question which one is accurate.

Is there any brand or known standard that you might be able to recommend?

Thanks

 

[rhervag]

i only have an old unbranded one that claims to be a standard 18% card + B & W.
just ordered a new one from gepstore on ebay because it has an additional mini 3tone chart in the center for macro work.
i hope it matches and will hopefully report good results.