That texture you see on the side may or may not be the conduit surface. Mine was actually from a power hungry extruder stepper. For some reason one of my steppers runs at .9v and it is smaller than the 2 steppers that power the x and y. Crazy but once I gave it more power, smoother prints. Make sure you cool the driver with a fan at that high of voltage and feel the stepper to make sure it isn’t too hot.