Also note that all the above applies to only the "D" lenses. The "C-mount" lenses on the H8 REX all use a larger screw on hood (33mm I think) with a series 5 filter. There is a thin hood and a thicker hood and they screw together for the 35mm and 12mm lenses. The 5.5 Rex lens only uses the thin piece.

So, to sum it up:

D-Mount (H8):
Yvar = series 4
Switar = Series 4.5

C-Mount (H8-REX):
Switar = Series 5