CF™660R succinimidyl ester (CF™660R SE) is a far-red fluorescent dye with an amine-reactive group (i.e., succinimidyl ester group). CF™660R is a bright and exceptionally photostable dye that absorbs at 663 nm and emits fluorescence at 682 nm in the borderline spectral region between far-red and near-IR. CF™660R is ideal for confocal microscopy, where it can add a long wavelength color in multi-color imaging.