Hi, I am going To share my opinion on syska power bank.
I have bought this power bank it has good Charging speed no doubt, If your handset support fast charging so it will give you fast charging. and about the battery back up its still ok not that good as they exclaim 20000Mah. I can charge my phone which has 3750mah battery backup only for 3 and half times in entire 20000Mah power bank and then it takes minimum 6-7 hours approx to be fully charged.
But It Has some defect every time USB port get stop working then if your power bank is in warranty then no problem it will be replaced by service center and which is going to take atleast another15days for replacement and not less then 15 days.
This problem occured in my power bank for 3 third time but now its out of warranty I cant replace it, Because they gives only 6months warranty.
For this issue I wont recommend anyone to buy syska power bank after paying 3.5K just for power bank & Every 2-3 months The same issue occurs.