The Behringer 121 Dual VCF is a 16HP Eurorack module that authentically recreates the classic 'System 100M' dual voltage-controlled filter design. Each of the two independent low-pass filters features three audio inputs with level controls, three CV inputs with attenuators, and a dedicated output. The module offers cutoff frequency and resonance controls for precise sound shaping, along with a switchable three-mode high-pass filter (Off, 1 kHz, 2 kHz, or 5 kHz) for added tonal versatility.