I used one of these as part of a DIY gravity filter as in
this site.
It was not a stellar experience.
.
My hydration tube was not a good fit for the filter: lots of fiddling around.
If you google around on "Frontier Pro" and "micron" you will discover some sites that state this filter filters down to 3 microns. That's actually quite large in the world of sick-making bugs.
I would strongly suggest that you chemically treat your water before filtering it.
Even though I managed to get the tube to stay on, and treated my water with aquamira tabs before filtering, I still got cryptosporidiosis on that trip. Could have been cross contamination, could have been a filter/chemical failure.
I don't know for sure, but I tossed that bad boy asap.
I have since switched to a First Need with an absolute particle retention of 0.4