Amazon.com : 52mm Pro Series Multi-Coated High Resolution Digital Ultraviolet Filter for Pentax smc DA 50mm f/1.8 Lens, Pentax DA 18-55mm f/3.5-5.6 AL WR Zoom Lens : Electronics
NiSi 52mm PRO Nano HUC UV Filter | NiSi Optics USA
Lens Filter Adapter Ring Gopro | Gopro Accessories Uv Filter | 52mm Uv Filter Gopro - Camera Filters - Aliexpress
NiSi 52mm UHC UV Protection Filter with 18 Multi-Layer Coatings UHD | Ultra Hard Coating | Nano Coating | Scratch Resistant Ultra-Slim UV Filter | NiSi Optics USA