Firecrest Cinema Neutral Density Filter (IRND)

Firecrest ND is a revolutionary new type of ND filter from Formatt Hitech. Rather than dyed resin, Firecrest is a rare earth mineral coating used to create hyper neutral NDs. The filters are made from 4mm thick Schott Superwite glass, and the multicoating is bonded in the middle to increase scratch resistance. Firecrest Filters are neutral across all spectrums, including UV, visible, and infrared.

Comes in 4x4", 4x5.65", 5.65x5.65", 6.6x6.6", 138mm, and 4.5".

What is the difference between Firecrest Standard, Firecrest Pro, and Firecrest Ultra?