I know nothing about these as I acquired them as part of a job lot, so they are sold as untested for spares repair only. You get 1x DM542 Microstep driver, 1x DM542T digital stepping driver, 1x Mach3 Interface board. I believe they are for CNC or other multi axis equipment, I genuinely have no means to test them so they are sold as untested.
eBay