They used to exists years ago. The company is no longer in business that made them. And they are very scarce finding them too. The ER series pretty much took over the Acura flex version of collets in industry. I have a collet holder I intend to make into a R-8 arbor some day. It's currently a NMTB #30 shank. All I have to do is make a threaded extension to screw into the drawbar end to accept the 7-16-20 threaded drawbar that the R-8 uses.