P{RS5} contains a functional w[+] marker allele, w^+mW.FRT.hs, which has an FRT site within the first intron. A second FRT site has been inserted downstream of the w^+mW.FRT.hs marker, in the same orientation as the FRT site in the intron.

P{RS3} and P{RS5} both contain the functional w^+mW.FRT.hs marker (which contains an FRT site in the first intron), plus a second FRT site. The location of the FRT site differs between the two elements; it is upstream of the marker in P{RS3} and downstream of the marker in P{RS5}. In addition, the orientation of the marker within the P-element ends differs between the two elements; in P{RS3} the order is P3'end - w^+mW.FRT.hs - FRT - P5'end, while in P{RS5} the order is P5'end - FRT - w^+mW.FRT.hs - P3'end.