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