Model BF PxP3CLSEF4 / BF PXP-3-CLSEF4. This is the 4mm thick highest quality version of this filter. Compare this glass in quality to Tiffen, Schneider, and B+W. Formatt 4 x 4" Soft Effects 3 Clear Filter produces clean, predictable, repeatable distortion effects for HD (High Definition) and are manufactured using a revolutionary process that essentially creates an optical distortion throughout the filter.