I have my main screwdriver that fits 90% of the screws I come across. Then there is the occasional really large or really tiny screw that I have to go find another tool to fit. The ones that are the problem for me are the screws that are just slightly too big or slightly too small. Those are the frustrating ones that wind up ruining my screwdriver or stripping the screw making it impossible to loosen or tighten. I need some sort of screwdriver that can temporarily liquefy and flow into the grooves of any size screw making a perfect fit every time.