The degree of protection against solid foreign objects is 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 amount of dust to penetrate under certain conditions. Dust-tight enclosures to numeral 6 do not allow any dust to penetrate.