“By robust, I mean something that isn't likely to break if accidentally dropped or break during operation.”
And
“Have owned or used the Sweetwater Gaurdian, First Need, Hiker Pro, MSR Miniworks (in clear water), MSR Hyperflow and another older Katadyn I forget the name of.”

If you have tried all those, I don’t think anything will please you.
If you drop any filter cartridge on a rock, it has a great possibility of breaking. But how do you know if it broke? You don’t. It still performs the same. The First Need however, makes brown water clear unless it’s broke; then the water is brown.

I’m willing to carry the 16oz filter for its nice pre-filter, speed, anti-air bubble, minimal part design (thus lower maintenance) and pesticide (etc.,) cleaning.
I just wish there was something that filtered tannic water (to produce clear water) that was lighter than the First Need.

“After our experiences with the Hiker Pro, I'll be selling mine and certainly wouldn't try anything that uses the same filter cartridge.”

That’s what all our scouts say too. We have scouts that are excellent with the nature of Shire Tarptents but fail with the Hiker Pro. In other troops, the Hiker Pro might be scout proof. Maybe it’s the pond and lake water we use. And that’s another reason our troop now uses First Need the most. And the cartridges are built like cannon balls--- so that helps with scouts.

-Barry, who psychologically can’t drink clean brown water (yet)