If the hashrate of the final delivered mining device is decrease than 16Gh, the real difference will probably be refunded according to $/Gh. When there is a dilemma Using the miner in 30 times of signing for shipping and delivery, the buyer may get a complete refund. Bitmain Antminers https://messiahwndqd.blogpixi.com/33354824/buy-bitmain-antminer-s19-pro-top-performance-for-bitcoin-mining