I've been looking at buying a set of Torx screwdrivers for taking small
things apart, the sort of screw that's 2mm across. But there seem to be two
notations out the

T4, T5, T6, etc
and
T0.5, T0.6, T1.0 etc (often they're quoted as T0.5x40, where I'm guessing
40 is the shaft length), such as these:
http://www.cricklewoodelectronics.co...cat=390&page=1

I understand the T4, T5 notation - I think the screws in my phone are
something like T4 or T5. But what does the other notation mean?
I'm guessing it might be something to do with the internal dimensions:
http://www.wihatools.com/torxspec.htm
in inches, but it still doesn't make sense. Perhaps T0.5=T5, T0.6=T6?

Thanks
Theo