The FB1750-500 from Thorlabs Inc is a Optical Filter with Wavelength 1750 to 6000 nm, Center Wavelength(CWL) 1.75 µm, Bandwidth (FWHM) 500 nm, Blocking Wavelength 0.2 to 12 µm, Filter Diameter 25.4 mm (1 Inch). More details for FB1750-500 can be seen below.