Slim frame is just 4.3mm (not inc rear threads). Lifetime Warranty. Ideal for Wide Angle Lenses. Number of coatings: 16. Hardened, Easy Clean Top Coat. Water, Oil, Dust, Fingerprint & Scratch Resistant. Under & Over Coated. Brass Frame. Schott B270 Superwhite Glass. No Color cast. Double Threaded Frame to allow stacking. Includes metal storage tin.