Win The Ultimate Park City Winter Weekend: Enter Now
When autocomplete results are available use up and down arrows to review and enter to select. Touch device users, explore by touch or with swipe gestures.


  • New Arrivals

Our Ski & Ride Guide—

The Top Picks Of The Season

MSRGuardian Purifier System

MSRGuardian Purifier System

Select a color:One Color

Select a size:


4.5 out of 5 stars
17 Reviews

Why We Like The Guardian Purifier System

Drinking straight from crystalline mountain streams is nice in principle, but a lot less awesome when we end up running for the bushes every five minutes for the rest of the trip. There are plenty of ways to prevent waterborne bummers, but none that we find as effective, easy to use, and reliable as the MSR Guardian Purifier System.

Developed for, and in conjunction with, the US military, the Guardian uses new Hollow Fiber technology to filter out just about everything (protozoa, bacteria, particulate, and even viruses), so you can sip fresh, clean water without fear. The Guardian has an easy pump-action design that can filter up to 2.5 liters per minute, and an ingenious self-cleaning design—10% of the water from every stroke flushes contaminants from the filter, so it never gets clogged or becomes less effective.


  • Pump-action purifier for backpacking and trekking
  • Self-cleaning design for easy maintenance in the field
  • Effective against protozoa, bacteria, viruses, and particulate
  • Water bottle adapter ensures convenient refilling
  • Cartridge life indicator lets you know when its time to replace
  • Item #CAS008I

Tech Specs

Purifying Element
Hollow Fiber
protozoa, bacteria, viruses, particulate
Pore Size
0.02 micron
Cartridge Life
10,000+ L
2.5L / min, 30/35 strokes / L
Field Cleanable
water bottle adapter, cartride replacement indicator
8 x 5in
Claimed Weight
1lb 1oz
Recommended Use
camping, backpacking
Manufacturer Warranty
limited 3 years

Overall Rating

4.5 based on 17 ratings

Review Summary

5 Stars - 13 reviews
4 Stars - 2 reviews
3 Stars - 1 reviews
2 Stars - 0 reviews
1 Stars - 1 reviews

Fits Small

Screen reader users: the following list provides a visual scale to illustrate the product fit. Please refer to the heading above for the fit type in text.
Runs smallTrue to sizeRuns large

What do you think about this product?


Selecting an option will reload the available reviews on the page

Sorry, we don’t currently have any of those types of reviews for this product.