Screw on protective cap to fit UHF female SO239 or UG363 Bulkhead adapter [Bulk] with 60mm chain that can be attached to bulkhead with a screw (not included) so cap is not lost when removed from fitting. fits UHF SO239 female socket type adapters or UG363 thru bulkhead adapter or socket 20mm outside diameter by 18mm high not including chain stud