Best of the rest
MSR sweetwater is the most versatile filter I have used. The filter itself is high quality and I do not hesitate using it for almost any water source. It also comes with iodine drops in case I travel out of the country. The stuff sack is compact and fits the brush, filter, nalgen adaptors, and platypus bladder that also came with the filter. Pens are great for ultralight packing, but for 3+ day treks I can't down sludgy H20. and at 11 oz, its worth using it full time.