MB 660R DBCO is a bright, photostable far-red dye that emits fluorescence at approximately 685 nm, located at the boundary between the far-red and near-infrared spectral regions. Although its absorption peak is near 665 nm, this dye can be effectively excited using 633 or 635 nm lasers. It remains stable across a pH range of 4 to 10. As a rhodamine-based dye, MB 660R DBCO shares the characteristic brightness and excellent photostability typical of rhodamine dyes.