This lens is compatible with the full JT Spectra family of masks including the world-famous ProFlex. It fits the Spectra, ProFlex, Flex-7, Proflex X, Premise, Proteus and Flex 8.
The dual-pane thermal lens prevents the mask from fogging. Great for low light conditions, woods or when it is overcast. Everyone should have a pair of replacement clear lenses in their bag just in case.