Transgenic construct used to study interactions between insulators. Consists of loxP cassette containing a 430bp gypsy\su(Hw)BR insulator, a FRT cassette containing the w eye enhancer (nucleotides -1084 to -1465 relative to the transcription start site), two copies of the 430bp gypsy\su(Hw)BR insulator, the y transcription unit, a mini-w gene.