FlyBase curator comment: The PBac{unk} entry in FlyBase is used to denote the transgenic construct present in an insertion when it is known that the inserted element corresponds to an engineered transgene where the transposable element ends are derived from the Tni\piggyBac element, but the particular transgene that has been inserted is not known or is unspecified.
Transgenic piggyBac construct, details not specified.