32 years as a t9 para, owned more chairs than I can count. I have 2 tiLits ZR's both with Surges. This is the 1st major invention in pushing technology that works so good you will NEVER be ableto be without them, and you will wonder how you lived without them so far. There is an inset along the rim that "effectively" holds a glorified rubber band. Its a thick, great feeling rubbery grip along the top, it gets better the more you use it. Im thinking I can get several years out of the band. Then order another band and replace it. If the entire rim is grippy you burn your hands when you stop, its was all or nothing. Now Natural Fit has done it and why no one figured it out before this is amazing, its like the iPod, obvious only after its created. The actual value of these rims in terms of making your life easier, saving grop tension, preventing carpul etc. is ten times the retail cost. All I can say is, thank you Natural Fit, Sincerely Thanks!