I have used both the 4L and 6L for hiking groups with scouts in tropical Australia over the last 5 years. I went from the 4L to the 6L only because I accidently lost the 4L! :-(It has high usage with up to 10 people using it over 2-4 day hikes, 2-4 times a year. I follow the long term storage instructions and the filter cartridge has tested fine prior to use in the following season.Without detracting from the 5 star rating, my two gripes are this:1. there should be another flow clamp on the dirty side of the filter for those occasions where 6L has been filtered but more water has been added to the dirty bag - this would allow flow to the filter to be stopped when the clean hose needs to be disconnected for use. As it seems the clamp cannot be purchased by itself ... MoreI have used both the 4L and 6L for hiking groups with scouts in tropical Australia over the last 5 years. I went from the 4L to the 6L only because I accidently lost the 4L! :-(It has high usage with up to 10 people using it over 2-4 day hikes, 2-4 times a year. I follow the long term storage instructions and the filter cartridge has tested fine prior to use in the following season.Without detracting from the 5 star rating, my two gripes are this:1. there should be another flow clamp on the dirty side of the filter for those occasions where 6L has been filtered but more water has been added to the dirty bag - this would allow flow to the filter to be stopped when the clean hose needs to be disconnected for use. As it seems the clamp cannot be purchased by itself (only part of a hose replacement kit), I have used a plastic clothes peg to crimp off the line as a solution.2. the zip-lock on the top of the dirty bag can be incredibly hard to squeeze shut and it is even more difficult for youth who are trying to do it. Sometimes if it isn't quite done, when the bag is picked up, it will pop open. A fold over system with a slider to seal the top as can be found on 'Osprey' water bladders, or the top of a dry bag would be a far easier design option to use in the field.Overall, an amazing, functional system.

I have had the 4L gravity system for 5 years now and just upgraded to the 6L system. I love this system. I do carry a backup filter and have had to use on one occasion due to my filter being clogged because I did not backflush at all for a couple of trips. I did backflush at a later date at home and this original filter was back up and going good. The original 4L dirty bag is coming apart at the top now but I have use so many times I feel that I have gotten more than my money’s worth. I have put this thing through the ringer for years. I do clean per the instructions included before storing. Another great thing about this system is you can carry water in the clean reservoir with a simple plastic bottle cap. I have done this several times on top of my pack when on ... MoreI have had the 4L gravity system for 5 years now and just upgraded to the 6L system. I love this system. I do carry a backup filter and have had to use on one occasion due to my filter being clogged because I did not backflush at all for a couple of trips. I did backflush at a later date at home and this original filter was back up and going good. The original 4L dirty bag is coming apart at the top now but I have use so many times I feel that I have gotten more than my money’s worth. I have put this thing through the ringer for years. I do clean per the instructions included before storing. Another great thing about this system is you can carry water in the clean reservoir with a simple plastic bottle cap. I have done this several times on top of my pack when on ridge’s requiring water to be packed in.I have tried some other methods and this is the best I have found. We typically hike 40-80 miles a year and this has been a wonderful asset out there.Happy Hiking

- Purchased for backcountry use.- Was previously using the Lifestraw Mission 12L.Pros:- Excellent flow rate.- Great quality.- Lightweight for a hanging system (weighed in at 353 g when packed)- For a hanging filtration system this requires only a small amount of space in your bag.- You set the filtration system up to filter the water into a reservoir instead of having to pass filtered water directly into your container. This allows you to set it up, leave, and return without the worry of overfilling your container. Just simply poor the filtered water reservoir into your container.- Other platypus bottles and reservoirs attach to this system.Cons:- Only 4L per reservoir. This will require refilling much more often than a larger bag such as my 12L Lifestraw ... More- Purchased for backcountry use.- Was previously using the Lifestraw Mission 12L.Pros:- Excellent flow rate.- Great quality.- Lightweight for a hanging system (weighed in at 353 g when packed)- For a hanging filtration system this requires only a small amount of space in your bag.- You set the filtration system up to filter the water into a reservoir instead of having to pass filtered water directly into your container. This allows you to set it up, leave, and return without the worry of overfilling your container. Just simply poor the filtered water reservoir into your container.- Other platypus bottles and reservoirs attach to this system.Cons:- Only 4L per reservoir. This will require refilling much more often than a larger bag such as my 12L Lifestraw Mission bag. Especially for larger groups. The flow rate is fast enough to make up for it but still inconvenient to have to refill it 4-5 times depending on water requirements and group size.- Pricey.- It’s a soft plastic to reduce weight so it’s more prone to damage than a harder plastic like a Nalgene bottle. That being said, I’ve had a platypus 2L bottle for a few years now and it’s in excellent condition. It’s all about how you take care of it.Overall this is a great filtration system for backcountry use in groups of 2-4 people (Depending on requirements). Worth the cost for the increased flow rate and weight reduction.