Turbo FTP Client is a free to use FTP client that includes in app purchases that range from $1.28 - $2.29 per item.
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Pro Material design
Turbo FTP is developed within the Material Design guidelines making for a nice looking FTP app on Android that has a familiar interface for anyone familiar with Material Design.
Pro Supports multiple FTP configurations
Turbo FTP client handles FTP, FTPS, FTPES and SFTP protocols, making for a wide array of configurations that Turbo FTP Client can work with, no matter the FTP it needs to connect to or share.
Pro Multiview support
For Samsung devices that can use the multiview feature, Turbo FTP Client can utilize multiple windows.
This app was last updated in July 2015, so there are potential vulnerabilities
Con Has low memory issues
Turbo FTP Client may run in to problems with a device running out of memory during a transfer, meaning the app will crash due to Android memory management. Making it difficult to successfully pull off transfers as well as use any other application during a transfer.