HARDENED GLASS
Hardened optical glass that has 4 times the breaking strength in ANSI standardized testing (ANSI Z80.3 : 2001) where a steel balls of varying size and weight were dropped from a height of 50 inches onto the glass.
WATERPROOF / SCRATCH & STAIN RESISTANT MULTI-COATING
Specialized coatings that are not just water-proof to repel water spots but also hardened to be scratch and stain resistant. Of course these coatings are from HOYA so they are greatly reduce reflections off the surface of the glass allowing you to capture more light in your photos.