5-(and-6)-Carboxy-X-rhodamine, succinimidyl ester is an amine-reactive long wavelength rhodamine dye. Derivatives made with the amine-reactive carboxy-X-rhodamine (ROX), succinimidyl ester are widely used for oligonucleotide labeling and automated DNA sequencing applications. Conjugates of this dye have longer-wavelength spectra than the spectra of Lissamine rhodamine B conjugates, but somewhat shorter-wavelength spectra than those of Texas Red® conjugates.