Transgenic construct used to study the enhancer blocking activity of the Zaf1 protein. Consists of an FRT cassette containing six Zaf1 binding sites, the w eye enhancer, a loxP cassette containing six Zaf1 protein-binding sites, and a w marker gene (the endogenous Wari insulator has been deleted from the 3' side of the marker to exclude the impacts of additional insulators).