htrahy Gel Cushion with Cover, Seat Cushion, Honeycomb, Zero-Gravity Design, Double, High Resilience, Cushion, Breathable, Office, Chair, Car, Home, for Desk Work Purchased on Amazon for 4980 yen. No longer needed after changing chairs, used for about 2-3 months, twice a week for work-from-home. There was a clear difference with and without it. Glad I bought it! Will upload actual photos later.