This one (1) Cable connects your Laptop/USB device to the Microsquirt ECM.  Instead of using 2 cables, (USB to Serial and Serial to 2.5mm),  this single 5 ft USB to serial to 2.5mm audio cable connects directly to the Microsquirt ECM.  We have personally verified this cable works on the Microsquirt ECM via to 2.5mm port and batch test each shipment  It uses the FT232RL chip which uses the native drivers in Win7/8/10, so there is no driver software to load.  If you purchase a USB to Serial Converter and and a Serial to 2.5mm, these 2 cables will cost $50 or more.  Amazon sells cables that are very similar, but the TX and RX is reversed and will not work unless your rewire your Microsquirt connector.  If your computer had the wrong driver forcefully installed by accident, you can use the factory website to find and load the proper driver.  Again... this is only for devices that are having a driver issue which is very rare. Contact us if you have questions.  https://ftdichip.com/drivers/vcp-drivers/ WE have sold more hundreds of these cables and all with perfect results.  This cable does work on MAC, but we do not support if you have issues.