From FabFilter Software Instruments:
FabFilter Micro is a lightweight filter plug-in. FabFilter Micro's single filter is smooth and creamy, yet easily turns into raw saturation and self-oscillation when tweaked using the interactive filter display. It features low-pass and high-pass shapes and an envelope follower to modulate the cut-off frequency.
With its individual Input Gain and Output Gain parameters, you can fully control the saturation of the internal filter, making FabFilter Micro not only ideally suited for basic filtering tasks, but also capable of beautiful distortion and analog saturation effects.