Bitmain Anthminer is presently very low price due drooping price of bitcoin and increased the the difficulty of mining, presently if you mine bitcoin you get 140 dollar per month with out paying electricity bill, and you get your initial investment within 6 month, it 6 month your get profit from your antiminer S9i.
Bitmain Antminer S9i-14TH/s is the world best bitcoin miner . The Antminer S9i is same size Antminer S7 . Antminer S9i is more than thrice power & twice the efficiency of the Antminer S7
Antminer S9i has 189 such chips to deliver powerful hash rate.
Antminer S9i’s Mother board has fast Dual ARM® Cortex®-A9 microprocessor with CoreSight™ and supports Gigabit Ethernet.
for purchasing link below:
https://shop.bitmain.com/
thank you 
antminer good option bitcoin mining