Ive used Prox for 30 years, until a couple of recent failures costing us big $$$'s, and finding out there not all made in Japan anymore, some made in China or Maylasia or something. Both failures where ring locators coming out after a few hours. Since then I've been useing Mitaka, a budget brand I Know, but I had been told there actualy manufacturerd in the same foundries as a lot of other more expensive brands ! (All I do is make sure I get the Japanese made ones) And we have not had any problems whatsoever, they even come with quality RIK rings too. So for now our bikes will carry on with these, albeit we change topends after a max of 10 hours. A piston kit costs us just £30 thats about $45. Wossner are very cheap here too, as are Namura's. I have not used either of those and dont know anyone who has, Vertex has the market share I'd guess and their excellent but expensive.