Mi{FlpTag.smV5.0} is designed to allow conditional gene tagging. It contains an artificial exon composed of a splice acceptor site, the smV5 tag and a splice donor site; this sequence can act as a protein trap element when inserted into a phase 0 coding intron of an endogenous gene in the correct orientation. The protein trap exon is flanked by two pairs of target sites for FLP-mediated recombination (FRT and FRT14), which form a flip-excision (FLEx) switch (design principles described in PMID:12665802), which means that the protein trap exon can be inverted using FLP recombinase and then stably locked in the opposite orientation, generating the Mi{FlpTag.smV5.0.lock} transgene. Mi{FlpTag.smV5.0} is generated in vivo by using a donor construct containing the FlpTag cassette flanked by attB sites to replace the RMCE cassette present in an insertion of a Mi{MIC} element in a coding intron of a gene of interest.