I have a complete set of inch and metric ER11mm collets. I had purchased them for my Sherline lathe and mill. I had sent my lathe head to be reworked for the ER11. I never got the head back. I had purchased a second head specifically for that purpose. This was several years ago and my memory is faulty. However, I had a receipt from USPS that it had been delivered but I never received it. Inquiring with neighbors revealed nothing. USPS did nothing as the return was not insured. Can't imagine anyone stealing it. Most people looking at it would not know what it is let alone have a use for it. Subsequently I purchased two different screw on collet chucks but neither were accurate. I decided to just do with 4-jaw chucks. I'm curious what your chuck is like. If it is a screw on chuck I hope they are more accurate than mine.