Aropey via Amazon offers Prime members its Aropey Aromatherapy Essential Oil Diffuser for $19.99. Coupon code "QMRYTL44" drops it to $12.31. Plus, Prime members bag free shipping. That's $2 under yesterday's 120ml version and $10 less than what you'd pay for that version now. It features a 160ml tank, LED lights, and automatic shut-off. Deal ends October 16.