If defective on arrival, the customer will receive a total refund right away and no return on the miner is needed. Immediately after dealing with electric power-hungry S19 versions for years, switching into the S21e XP Hyd 3U was like breathing contemporary air. I ordered a few from antminers23hyd.com https://stephenrjtlr.buyoutblog.com/39422295/what-buyers-should-know-about-antminer-s19-pro