There are many power banks in the market of different mAh and of differen costs and of different companies.nowadays everyone needs fast charging.and there are many power banks that provide fast charging.i have used MI power bank.it is not so costly.and very fast charging.but not so easy to carry.i have also used portronics power bank.it is easy to carry.provides fast charging and has a long battery life.it’s cost is 900 for 10000 mAh and MI power bank is 1700