This Cokin Z-Pro 007 Infrared Filter is for black and white infrared film when you only want to transmit the infrared spectrum and none of the visible spectrum.
Z-PRO Filters are made of CR39 Resin which is a reputable lightweight and shock-resistant optical material also used for ophthalmic glasses. The Z-PRO Series is recommended for focal lengths of 20mm onwards (in the 35mm format).
Note:
This filter is round and fits the Z-Pro Holder