Ikelite UR/Pro Blue Water Color Correction Filter for 4.2" Diameter Port Package Includes:1 x UW Red Filter,1 x Lanyard Compatible With: Ikelite For tropical blue water settings. Enhances warm reds and oranges with available sunlight up to 80 ft. (24m). This filter is usable on any 4.2-inch (106 mm) diameter housing lens port. To check compatibility with Ikelite housings, please refer to the housing instruction manual or webpage.