Phone Holder The one closest to the filter holder housing is the narrowest; it allows the use of round filters with notched edges (polarizer, star filters..). The two central slots are intended for square filters. The outer slot can be used either for an additional filter or for a coupling ring. Multi function card, can be installed in any filter Backed with DigitalGoja 90-Day 100% Satisfaction Guarantee. Lightweight filter holder allows the use of 4x4 or 4x5 (100mm) filters to be attached to camera lens Goja Brand. zomei. Manufactured to meet the highest standard of desi Produc gn and quality.