I own a Vsr, and I have ripped the hop-up rubber. For my setup it is best to not have a nub protruding that makes contact with the bb (I'm using a SCS), so this leads me to this question; besides aligning the barrel, how is a hop-up rubber any better than a ordinary rubber sleeve? If I found a way to keep my barrel aligned (which is normally done by the multiple nubs protruding from the rubber) why couldn't I just get many different types of rubber sleeves of different hardness and materials from any hardware site, test them out and find out which material is the best for my setup at a much lower cost than buying 'real' hop-up rubbers. Plus, once a certain portion of the rubber wore out, I could just rotate it to a new, fresh section. Is there something I'm missing?