Abstract: In order to improve a functional part, in particular a fitting, for example for a housing, comprising a connection receptacle or a plurality of connection receptacles, wherein the connection receptacle or each of the plurality of connection receptacles is configured to receive a connection mating piece of another part, in particular a connection mating piece of a housing part, in particular in the form of a bayonet closure in order to securely and releasably connect the functional part to the other part, it is proposed that the one connection receptacle or at least one connection receptacle, in particular some or each of the plurality of connection receptacles, is configured to receive connection mating pieces of different sizes, in particular so as to produce a secure connection.