I had a camping trip planned so I looked at something that would hold a good sized sleeping bag. I bought this waterproof Givi for $95. Nothin fancy, but it will keep your stuff dry. It will expand to hold quite a bit of gear. I had a big sleeping bag along with my clothes for three days and still had room. It was easy to fit. It went well on the rack (if I wanted it dead center, I had to remove antenna. No biggie as I usually use the ipod). It was a homerun on the back seat as I had it worked where it doubled as a backrest. It has some nice tie down points so very flexible mounting.
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