The first number represents protection against solid objects as well as user safety
0 = no protection
1 = protected against objects of Ø50 mm or larger, and effective against large surfaces of the body, i.e. the back of the hand
2 = protected against objects of Ø12.5 mm or larger, and effective against fingers or similar
3 = protected against objects of Ø2.5 mm or larger, and effective against tools, thick wires, etc.
4 = protected against objects of Ø1 mm or larger, and effective against most wires, thin screws, large ants, etc.
5 = protected against dust
6 = dust-tight