Reganwrote a review of Platypus GravityWorks 4.0L Filter System on August 4, 2017
Familiarity: I've used it once or twice and have initial impressions
I have used this a couple times backpacking in Kentucky. It filters high volume at great speed and is lightweight. Murky river water came out clear (and safe, I assume, as we did not got sick.) The wide opening helped capture a trickle from a rock overhang. So far so good.