Flat ports are recommended for standard macro and telephoto lenses due to refraction flat ports reduce the angle of coverage of a lens and magnify the image this makes the flat port ideal when using standard macro or zoom lenses to shoot small subjects note that if a port is long enough to accommodate the full length of a 11 macro lens the lens may vignette when used at infinity if access to the lens full range is desired then select a dome port instead accommodates lenses up to 45