I bought this water filter straw for our emergency first aid kit that we take with us when we hike and camp in the backcountry. I think I would still use our Katadyn filter system as my primary filter, but this is excellent for shorter hikes.
According to the paperwork with this, this filters out 99.9999% of colibacillus, legionella, 99.99% of Giardia Lamblia and cryptosporidium.