The TL-Smoother is an addon module for 3D printer stepper motor drivers.
The board provides flyback diodes for the motor outputs, so that they are also protected against voltage ripples, especially when transitioning between intermittent ON and OFF states. This can result in visible artifacting/ringing in prints.
These are recommended especially for 3D Printers using DVR8825 and A4988/2 stepper drivers.
Each TL Smoother comes with a 20cm 4-pin extension cable to bridge the connection between your mainboard to the TL Smoother to your stepper motors.