4.33" Acrylic Wide-Angle Dome Port ~for Canon EF-EOS M Adapter and EF 8-15mm f/4L Fisheye USMThis wide angle dome port is part of the N85 port system, features an acrylic element and anodized aluminum construction and is specific for use with the Canon EF EOS M adapter and EF 8 15mm f 4L Fisheye USM, with a knob for zooming (requires optional zoom gear). Technical Specifications Depth Rating 100m Port System N85 Weight Port Opening Diameter Port Diameter 4. 33" Body Material Anodized Aluminum Alloy Port Material Acrylic Port Coating Port