Degrees of protection against solid foreign objects indicated by the first characteristic numeral. The protection against the ingress of solid foreign objects implies that the object probes up to numeral 2 shall not fully penetrate the enclosure. This means that the full diameter of the sphere shall not pass through an opening in the enclosure. Object probes for numerals 3 and 4 shall not penetrate the enclosure at all. Dust-protected enclosures to numeral 5 allow a limited quantity of dust to penetrate under certain conditions. Dust-tight enclosures to numeral 6 do not allow any dust to penetrate.