PolarPro "Frame" Glass Polarizer Filter for GoPro HERO3 / P1005
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Amazon.com : Underwater Housing Red Filter for GoPro HD Hero 3 : Underwater Camera Housings : Electronics
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GoScope (60M) Red Filter - Compatible with GOPRO HERO4 / HERO3+ / HERO3 Dive HOUSING (60M Case Only) Laser Cut Optical Red Filter {See Pictures to Make Sure This FITS Your Camera CASE} : Electronics - Amazon.com
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PolarPro Venture3+ Filter Set for GoPro HERO3+ Housings P1015