The phot r purple camera lens filter for the gopro hero 4 3 and 3 attaches on to the dive housing of the hero 4 3 and 3 purple filters are ideal for use in fresh water such as lakes reservoirs and green water solid colour filters are designed to enhance natural light with subtle colour wash or bold strong effect the filter snaps into place for quick tool free installation and features scratch resistant optical grade glass to ensure optimal image claritycapture your best every footgage