Free: Contests & Raffles.
I like my pen. Much prefer it over a pump unless I know my water sources are gonna be "gritty". I've had to chew my water a time or two and it's not my favorite thing to do I use aquamira drops more than anything these days. If I didnt die from the water out of the beaver crap filled ponds in NV last year I'm certain that all of the above methods will work
I've used on never a problem. I put a cloth or something over mouth of nalgene keeps the big chicks out.