I don't really sell, but whenever I mail a poster as a gift or something, I roll the poster tighter than the tube and roll a piece of 8 1/2 x 11 white paper at the end. I then tape the paper so it remains rolled tight around the poster. I make little cut at the end of the paper, fold them back inside the rolled poster to protect the end. I then stick it in the tube, place paper towels at each end, and it's done. I've never had a problem with it, it's much easier than sticking the poster in a sleeve and it only cost you 2 pieces of paper and a little tape.
My 2c.
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