These fit over a variety of shoes and boots for me, stay in place all day, keep junk out of my shoes and are (on average) as water-resistant as whatever's left of the gore-tex shoe lining at that point in the season. I should splash around in fewer puddles if I expect dry feet. They're great gaiters!
OR is serious about the lifetime warranty. After a lot of side-hilling on rocks and scree, the buckle prongs bent and eventually broke off. The rest of the buckle looked like it'd been ground in a kitchen garbage disposal for a few hours. Interestingly, the underfoot straps were still going strong, and the rest of the gaiter was as good as new. I think that means that other than the buckles, these things are close to indestructible.
The OR rep was helpful and quick to offer to a replacement or repair. I was worried that the replacement wouldn't arrive in time for the next trip, so I bought another pair of the same gaiters. However, the new ones arrived eerily fast, and now I have two pair!
Strangers on the internet are probably not the best source for survival decisions.
That said, you can find emergency water treatment information from the Red Cross, FEMA or other reliable sources that will tell you that by starting with clear water, the correct quantity of sodium hypochlorite (the active ingredient in this product and in unscented bleach, albeit at different concentrations), and waiting 30 minutes, you will have water that is safe to drink. (Except for heavy-metal or other chemical contamination.) One piece of advice you'll see repeated is that the water should smell slightly of chlorine immediately after treatment.
Anecdotally, I have been told that this protocol is weaker against cysts like cryptosporidium, so if you're using a water source known for this risk, you'd want a water filter.