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 1:1 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 6.1-inch (15.5cm) long and 3.3-inch (8.4cm) in diameter. Measure your lens or use Ikelite s Port Finder chart on their website to determine compatibility.