We purchased 5 Hiker Pros for the Scout Troop a couple of months ago and used them heavily in South Dakota in July. Personally, my wife and I use a Guide. All came with a separate ziplock bag for all clean side parts (hose, bottle adaptor, bladder adapter, etc). All instructions are quite clear about keeping the clean side stuff away from the dirty side stuff. No faults with any of that.

Our current scouts have never had any water that didn't come out of a spigot or faucet before this trip. I'm happy to report that they broke nothing, lost nothing, and cross-contaminated nothing. We did have to tear down two of the Hiker Pro filters after the trip to address clogs from sucking in to much junk - simple cleaning per the instructions and both working fine now. Flushed all with bleach water after the trip, again per instructions.

On our Guide, we went with the CamelBak hydration pack adapter (requires a parts change on the bladder hose) - that is THE way to go! One of the Hiker Pros was temporarily set-up for that as well (simply pulled off the part on the filter hose after the trip) - that particular crew all used Camelbak bladders and invested in the parts.

The Guide WILL screw directly onto a water bottle a la MSR, using a supplied replacement part. All 6 of the filters came with a non-screw-in water bottle gizmo that works very well.

Although it was nice to have help, no one had any trouble managing either model alone.

General fund: The First Need filter is US EPA certified to get viruses out as well - by filtration. There are bottle-based filters that still use post-filtration viricide cartridges (probably iodine based). For the rest, post - filtration chemical treatment (chlorine, iodine, chlorine dioxide, etc) will nuke viral contaminents if they are a concern, (Pre-treatment does as well, but my preference would be for post treatment).

We were extremely pleased with the performancce of the filters AND the close attention the inexperienced scouts paid to their proper use. We took a re-build kit and spare filter with us but did not need either. Probably will add an MSR Sweetwater pre-filter to the input hoses of these before the next major trip to make them a little more resistant to accidental ingestion of mass quantities of algae and/or mud and will possibly come up with a modified nipple cover for the output nipple - we didn't lose any this trip, but with the boys it is likely we will unless we tether the cover - and we want to keep that sanitary for obvious reasons.