This filter set is ideal for use with Cy3™ and a variety of other orange fluorophores (including DsRed fluorescent protein). It is optimized to provide the highest brightness, while maintaining a very high signal-to-noise ratio. Are you co-labeling with YFP, GFP, or FITC? In order to substantially eliminate green-fluorophore bleedthrough we recommend using our TRITC-B filter set. For mercury (e.g., HBO) lamp users labeling with Cy3 the single-fluorophore signal-to-noise ratio will be slightly higher, and the brightness slightly lower, with the TRITC-A filter set. Xenon lamp users of the TRITC-A filter set who are labeling with Cy3 will enjoy a significantly enhanced signal-to-noise ratio and reduced photobleaching in exchange for brightness.