The Redolent Plus Dual Diffuser is our largest home scenting diffuser. This diffuser comes with two 500 ml refillable bottles. A single bottle can scent up to 3000 square feet and double bottle scent up to 6000 square feet. This is a waterless and heatless system that connects to your HVAC system in minutes. The programmable timer allows for flexibility in scent distribution frequency. The Redolent Plus Dual Diffuser unit is pet and kid safe. Available in black only.