A snRNA:U6:96Ac ( U6:3 ) promoter drives expression of a dual-gRNA targeting EGFP and GFP, separated by a Drosophila tRNA-Gln (Q) spacer. The 2.1 gRNA scaffold (which includes an additional extension of the second stem loop compared to the (F+E) gRNA scaffold described in FBrf0241409) is used. This is followed by a Ubi-p63E promoter driving expression of mTagBFP2.