Lenses - EAO 31 Series A selection of round, square and rectangular lenses in various colours suitable for use with the EAO 31 Series of illuminated push button switches and indicators. Each EAO 31 Series lens has a flat flush profile and is manufactured from Polymethyl Methacrylate. Lenses can be engraved, hot stamped or used with film inserts, apart from the white lenses 248-5510 and 248-5504 which are not suitable for use with film insert labelling.