1. Available in High performance Brass or rugged Aircraft grade Aluminum filter rings . 2. Brass filters use 1.5mm thick top quality American made Corning Glass: Aluminum filters use 1.1mm thick high quality German manufactured Schott Plate Glass B270. 3. All filter rings provide high strength, corrosion resistance, stability and critical filter alignment. Brass rings provide enhanced strength and stability. 4. Brass filters have L41 coatings and aluminum filters have L37 coatings on each side of the glass (waterproof, oil-resistant, scratch-resistant, anti-reflective, anti-static) for easy cleaning and superior lens protection. 5. 22-layer anti-reflective coatings on both surfaces eliminates reflections and provides light transmission of almost 100%. 6. Extremely thin ring (only 3.4mm) prevents vignetting even with wideangle lenses (f=16mm)