Filter for 300 f2.8 mk2

Is the Canon 52mm Drop In Circular Polarising Filter CPL, PL-C52 (WII) the best option for my 300mm f2.8 mk2 ?

Thanks

If you're looking for a CPL filter there's really only 2 functioning options, the PL-C 52(old version) and PL-C 52 WII(new version). My guess is the WII has improvements but I've tried to research and ask what the differences are and have came up empty. I have the old version and works as it should. You could also put a 52mm screw in CPL on the 52mm screw in filter holder but you couldn't rotate the CPL w/o pulling out the drop in holder.

I don't know what the differences between the old and new PL-Cs are either; however I have the 300 2.8 IS Mk. I and the 500 f/4 Mk. II and the PL-C 52 WII fits in both of them without any obvious issues although neither is on the compatibility list at Canon USA for that particular filter. (The gel holder that came with the 500 was the WII, though the 500's not on the compatibility list for that, either)