The phiC31 RNAi library (KK) was created using the phiC31 integrase system to target RNAi transgenes to a specific landing site on the second chromosome. This insertion site (P{attP,y+,w3'}VIE-260B) was selected based on its low level of basal expression and consistent high level of GAL4-dependent expression across a range of different tissues. The RNAi transgenes consist of inverted repeats that were designed to reduce the risk of off-target effects. Additional information about the vectors used (pKC26 and pKC43) may be found on the VDRC website. The genomic position of the landing site insertion P{attP,y+,w3'}VIE-260B has been determined to be 2L:22019296 . Descriptive statements about off-target and multi-target information correspond to the following parameter ranges: For specificity (off-target effects; s19 = Specificity score) If s19 =< 0.5 "Probable off-target effects." If 0.5 < s19 =<0.8 "Possible off-target effects." If 0.8 < s19 < 1 "Possible off-target effects (low probability)." If s19 = 1, no comment For multiple on-target genes (K = number of on-target genes) If K > 1 AND s19 > 0.5 "Targets multiple paralogous genes." If K = 1, no comment