MSR's Trailshot brings new convenience to the task of water treatment, its designed to be carried in an external pocket so that it can be depoyed instantly when the need arises.
Its effectiveness in removing bacteria and protozoa is in-line with other filters in this category and is detailed elsewhere, suffice to say that it meets U.S. EPA drinking water standards and NSF protocol P231 for removal of bacteria (99.9999%), protozoa (99.9%), and particulates.
Where this filter scores over any others that we've used is its ease of use. The filter cartridge is housed inside a flexible bulb that acts as the pump, at the top is a spout which is where the filtered water comes out, at the other end is a tube with a small pre-filter unit on the end.
To use the trailshot you simply need to immerse the pre-filter in water and pump the flexible bulb with one hand to suck the water into the bulb. Once the bulb is full further pumping forces the water through the filter and out of the spout. We found the flow rate to be excellent and on first use filled a 2 litre Platypus in what seemed to be a few minutes.
It does have some performance nuances though - occasionally the pump seemed to stop pumping water through, the solution was to re-start the process. We also found that it worked much better if the inlet pre-filter coud be aligned with the water flow - so if we were filling up from a flowing stream we could use the force of the water to help the process.
The worst water we accessed was when climbing a rounded hill with a stream of water flowing down the centre - it had no depth to it but we were dry so we dug a small hole to create pool and filtered from there - the Trailshot performed flawlessly.
One of the key features of the trailshot is the method of backflushing - backflushing is required on all filters as the filter itself will clog with matter removed from the water, the process may be quite involved on some filter units but the Trailshot is the best we've seen, you simply remove the inlet tube, give the fiter a shake and squirt the water back out of the inlet connection. This is so easy we did it after each use, keeping the Trailshot in tip top condition.
We think the Trailshot is a real step forward and we're not the only ones, there's a lot of interest in the product.