How is a Phillips screwdriver size determined?

How is a Phillips screwdriver size determined? cross slot screwdriver No 1 x 80mm 1kV Expert VDE Cross Slot Screwdriver Expert Quality, tested to 10kV, Suitable for working on live circuits of 1kV AC and DC Chrome cross slot screwdriver KNIPEX Cross Slot Screwdriver is ergonomically optimized dual component handle for fatigue reduced work and optimum transmission of force Tip burnished, with

cross slot screwdriver Precision Screwdriver Set Made with Chrome Vanadium Steel, Also Features Soft Grips for Comfort 2 X Cross Slot Sizes: , ASDA Product Information

crossslot keys in request don''t hash to the same slot Heyco 4511002033 4511 2 VDE-Cross Slot Screwdriver HEYCO, Tools & Home Improvement, US-B077W2CYBQ, 4024089165517, 4511002033  KNIPEX Cross Slot Screwdriver is ergonomically optimized dual component handle for fatigue reduced work and optimum transmission of force Tip burnished, with