Class 4 black hole
A class 4 black hole was a type of black hole. 

By 2152, according to the Vulcan star charts, the Vulcans had surveyed more than two thousand of these astronomical objects. In that year, the  discovered one of them in a trinary star system, a feature which hadn't been discovered by the Vulcans before. ()

4 black hole, class
Class 04 black hole