Lens, Visor, Flying Helmet, Neutral Dark [XL: PN 51D3643-3], [LG: PN 51D3643-2], [MD: PN 51D3643-1]. We have these in used condition and a few unissued condition w/ wax coating on lens. We have 4 sizes in stock for use on sizes Extra Large, Large, Medium, or Small P-3 & P-4 series helmets. The size is visor size and does not have to match the helmet size. XL NSN: 8475-00-212-1954; LG NSN: 8475-00-212-1955; MED NSN: 8475-00-212-1956