The pP{Target} series vectors are for use in the ends-in targeted gene replacement method of Rong and Golic. Each has a polylinker, white marker gene, and I-CreI site, flanked by FRT sites and P element ends. pP{TargetB} is a smaller version of pP{Target}. For more information please see this website: http://sekelsky.bio.unc.edu/Research/Vectors/Vectors.html