I carry mine in my bag (when I remember) and I find they are useful sometimes, for example, if you want to know what coloured blood bottles to use or to remember some of the nemonics.
Mine were a free gift with a magazine subscription, but I don't think I would pay around £20.00 for a set.
KS x

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Kentish Spitfire
Moderator, Student Services
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"It's better to be thought a fool - rather than proved a fool!"