CruzQuench™ 4 CPG 500 Å is designed to be a superior quencher to ROX, CFLsm4 and Texas Red®. CQ4 has (a). much stronger absorption; (b). much higher quenching efficiency; and (c). versatile reactive forms with desired solubility for labeling oligonucleotides and peptides. This CQ4 product is primarily used for the in-synthesis labeling of oligonucleotides.