For clarification: 1 by 1 means when i receive 1 USDT i send 1 coupon. In case anyone is concerned about being scammed.

i do have more coupons but they are expiring soon "1. The coupons will expire at December 31st 23:59:59, 2020 (GMT+8)."

i have 1$ x50  of those. They say they are for S17 and T17 series. But when placing an order for current S19 series system accepts them ( initial accept, havent proceeded to checkout yet ).