These are VERY RARE and VINTAGE "PROCOMP" filters ...
Designed back in the very late 90's and used on several major productions where green screen or blue screen were involved, and where NO FRINGING was allowed by VFX
This is an extensive and complete kit:
7x +15Cc green screen
7x +25Cc green screen
7x +15Cc blue screen
7x +25Cc blue screen
7x clear SFX filters with various grids, to be used on backgrounds and plates
Using blue or green screen, you have to use +15Cc or +25Cc (depending on the lighting and color fringing), and then choose a density depending on your focal length
Then, to match your background (plate) you have to use the same filter density, but on a clear glass.
a DVD is delivered with all instructions of use.
Those filters are MINT, NEW, only used twice, do NOT exist anymore !
They use to cost a fortune, the list price for those 35 filters-set was over € 6,000
SOLD AT A BARGAIN PRICE: € 2,000