CWDM channels wavelengths bandwidth

CWDM wavelengths have 18 CWDM channels from 1270nm to 1610nm, 20nm gap between adjacent central wavelength, the cwdm bandwidth of central wavelength is -6.5nm to 6.5nm.
HyOptic passive CWDM filter bandwidth is -7nm to 7nm or -7.5nm to 7.5nm, that big range bandwidth can meet different requirements.