The S, ZETA and ES series stepper motors have been discontinued.
These were all the same step motors and had a 10-foot cable as standard. The ZETA motor came with a ZETA drive connector on the end (screw-terminal), the S motor came with a S drive connector on the end, and the ES step motor had no connector.
All custom products based on the above parts will also be discontinued, for example:
As reference, this had been announced October 2018, effective April 2019. Inventory remained after last time buy and different size motors ran out at different times.