which filter would you get for 135mm F/2L?

ontopofm wrote in post #10230283
I want to keep this lens for a long time and would hate to see dust get inside the glass

Covering the front element of this lens with a filter will not keep dust from getting in. The front element is pretty well sealed as it is. Not at all like a 17-40 where the front element moves in and out while zooming and mounting a filter will provide some measure of sealing not present without one.

windpig wrote in post #10231784
also works as an ND filter on the sunny days when you want to shoot as wide as possible. I'm not sure what the OP will be shooting with this lens, but outdoor portraiture, weddings, etc would tend to have a need for a CPL.

Yes it will be used for indoor/outdoor portraiture and friends weddings. Looks like the CPL will have more use and that is what I will be getting. Thanks guys