I threw this into the pocket of my pack and, fortunately for my feet, haven't had to use it yet. It's small and lightweight and seems to have everything I'll need.

This summer(2004) I did the wonderland trail which goes AROUND Mt. Rainier, 100 miles, 12 days, 20,000 feet of elevation gain and loss.
A quarter mile from camp on day 2 I got blisters on BOTH my heels even though i had logged over 80 miles, a lot of vert, and a lot of time wearing these boots. By the way, Lowas rock!! I developed a couple more small ones later on in the trip in various spots on either foot. Did it slow me down or put a halt to my trip? HELL NO!!! I had the blister pack!! The second skin is amazing! A little gel pack you put on under the moleskin. Even on my heels being such a high abrasion area made little difference. I experienced really slight discomfort initially as the blister was so fresh but it was very short lived, within 15 minutes I forgot I even had any blisters. Bottom line: if you hike at all you should have one of these little lightweight wonders in your pack, if you use it even once it will pay for itself. It's also great to have if you hike with people who are less active or unprepared. Do you really want to turn back when you are so close to your destination because you or one of your party got a little blister? I wouldn't and i don't think you would either, just get one! Buy your buddy one too so he/she doesn't have an excuse! Now get out there and get to hiking!!!!!