Typically FbFPs have an excitation maximum at a wavelength of approximately 450 nm (blue light) and a second distinct excitation peak around 370 nm (UV-A light). The main emission peak is at approx. 495 nm, with a shoulder around 520 nm. One variant of Pp2FbFP (Q116V) exhibits a 10 nm blue shift in both the excitation and emission spectra. Rationally designed variants of iLOV and CagFbFP exhibit 6 and 7 nm red shifts, respectively.