I have a steripen adventure which uses cr123 batteries, the only one to stay away from is the Journey (newest one with LCD screen). The Journey is having alot of issues and I think the LCD screen is just a battery consumption anyway. The traveler and the original (AA batteries)are good as well. It depends on what you want, the CR123 adventure and traveler are very compact but if you leave the batteries in them for long periods of time (days), then the batteries will slowly run down. I usually treat the water and take one battery out of it to prevent the small drain on the battery's. The original (AA) uses standard batteries but is big and bulky. I would suggest a adventure if you like small and compact or the original if you want to stay with AA batteries. In a pinch you can run the adventure 100% off of a 40 watt solar cell without any batteries, I haven't tried the original.

http://www.steripen.com/steripen_products.html

Stay away from the Journey (bellow)



Good ones are bellow

Adventure



Traveler



Classic (original)