Optical filter orders go wrong when the specification is incomplete. Use this checklist to describe exactly what you need.
Define the spectral shape
State cut-on/cut-off wavelengths for edge filters, or centre wavelength and FWHM for bandpass.
Set the blocking level
Specify optical density (e.g. OD4 or OD6) across the rejection band, not just in-band transmission.
Angle and substrate
Note the angle of incidence and choose a substrate — optical glass or fused silica — that suits your environment.