Hiker Pro information in Jeff's answer is all correct-----except Katadyn Hiker Pro is still in their lineup. The Hiker Pro sells to the more techy user and the Hiker to those that like the simplest, most idiot-proof: fast, lightweight, durable filter.

Hiker Pro is a upgrade. 1. It comes with three adaptors that you can use to pump into a Camelback bite-tube. 2. It has a quick release for the inlet hose so you can put it into a included sealable bag and isolate the dirty drippy water end from the rest of the system. 3. Most importantly: it has a field-maintainable "Filter Protecter" that wraps around the pleated glass fiber inner filter. When this clogs with sticky algae, which can trash the inner filter, you can clean the "Filter Protecter" with an included sponge. Works well enough that Backpacker Magazine's Gear Lab gave the Hiker Pro the title of "World's Toughest Pump Filter". I think Katadyn has eliminated the Hiker Pro from their lineup. I couldn't find it anywhere on their website. If you're thinking about purchasing one, you might want do it ASAP!http://products.katadyn.com/brands-and-products/produkte/Backcountry_Series_24.htmlhttp://www.backcountry.com/store/EXT0046/Katadyn-Hiker-Pro-Water-Microfilter.html