The 42-5041-000 from Ealing Catalog is a Visible Bandpass Optical Filter that has a central wavelength of 400 nm. It has a bandwidth (FWHM) of 10 nm and a minimum peak transmission of 40%. This filter uses optical quality glass substrates and has an aperture of 8.7 mm. It is available in a hermetically sealed package in a black anodized aluminum ring that measures ∅12.7 x 6.4 mm.