Eowpower500Pcs White Nylon Flat Washers Assortment Kit for M2 M2.5 M3 M4 M5 M6 M8 M10 Screw Bolt

Can u use this for air gun repair for the co2 pistol seal

Can you use on screws that are too long for a dresser knobs?

Can I use this for my mechanical keyboard case screws?

Are these washers exactly, 4, 5 ,6mm inner diameter or are they a little more to fit bolts and shafts that are exactly, 4, 5, 6mm?