On 13/01/2015 22:25, Arras wrote:
I want to get some Phillips screwdrivers for very small screws.

Most suppliers quote something like this:
"#0 and #00".

However others quote things like this:
"7 Heads Phillips 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0".

How can I work out which is equivalent to which?

It's a continuous range of sizes, where the smaller ones have
(presumably) been named after the main series: PH 1, 2, 3, 4 are the
'normal' woodscrew sizes but PH0, 00 and 000 are the smaller sizes that
you find in things like laptops.

The smaller ones are normally found in kits such as :
http://www.toolstation.com/shop/Hand...ver+Set/p12357

(That's item number 12357 at Toolstation to illustrate, not as any kind
of recommendation!).

If you have an application that's in the least demanding, you may well
find a cheap set will become mangled on the first use, so it's worth
looking around for some half-decent ones.