Hi! T stands for Torx, so if you say there's a T3 you need a Torx number 3. It's like when you hear Philips etc, Torx is just a different kind of screwdriver. M2 M3 etc is not about the screwdriver, is just a measure of the screw itself, it means its diameter is 2mm (M2) or 3mm (M3) and so on.
Battery replacement screwdrivers. I bought from Dell a refurb battery for my laptop. As the machine is over 4 years old no original batteries they only sell refurb ones.  Reading the Dell info on how to replace the battery I know I need screwdrivers for these four types of screws. M2x2   M1.6x4   M2x3, Torx   M1.6x6 Does anyone know where I can buy them please, everything online either does not detail what is in the set or talks about T 3, T10 etc not the name I know the screws by.  Arrrgghhhhhh.  Thanks for your time, hoping someone has an idea or can advise which T value equates to each screw.
Battery replacement SCREWDRIVERS for XPS 13 9360