A 20cm or 8 inch (approximate aperture size), opening porthole made in a classic style, using traditional methods, to shipping industry standards.
A 26cm or 10 inch (approximate aperture size), opening porthole made in a classic style, using traditional methods, to shipping industry standards.
A 30cm or 12 inch (approximate aperture size), opening porthole made in a classic style, using traditional methods, to shipping industry standards.
