I think I am not understanding what you mean by "robust."

Are you meaning it will filter anything? If you are filtering very muddy water, you can always pretreat it with a flocculant to settle out the particulates. Prefilters help a lot too.

If you mean unbreakable... I have yet to see a filter that is not breakable - the Pocket is no exception. All of them have plastic housing after all. I'd have to say the filter least likely to break is my gravity filter - a bag made of waterproof nylon with a filter inside it. I can take the filter out and use it for a shower, too.