This heat wave has turned me into a hydration gremlin, clutching my water bottle like it’s a life source—which, to be fair, it is. But here’s the thing: your favorite trendy water bottle is only as good as what’s in it, and out on the trail, that last sip comes faster than you think. Enter the LifeStraw Personal Water Filter, down to just $9.99 for Amazon Prime Day (running July 8-11). Remember, if you don’t have an active Amazon Prime subscription, you can sign up for a free 30-day trial here. This recorder-sized miracle protects against bacteria (including E.coli and Salmonella) and parasites (like Giardia and Cryptosporidium) and filters out debris.