HEX NA NHS ester is a pink fluorescent dye producing a stable fluorescent signal in bioimaging. Optical properties of HEX NA are similar to that of HEX, JOE, VIC and Cal Fluor 560. The excitation and emission maxima of HEX are at 534/549 nm. NHS esters readily react with amino groups of biomolecules such as the ε-amino group of lysine or the amine termini of modified nucleotides to form stable amide bonds between dyes and biomolecules. We offer HEX NA NHS ester for labeling biomolecules and amino-modified oligonucleotides in solid phase oligonucleotide synthesis.