This European Standard specifies the characteristics of protective covers for receptacles in the family of circular electrical connectors with triple start threaded coupling. It applies to models in Table 2.For receptacles, see EN 3645-003, EN 3645-004, EN 3645-005, EN 3645-009 and EN 3645-010 respectively. These connectors are derived from and interchangeable with models W, F, K and Z in MIL-DTL-38999/33.