Big!

The Download Block supports pretty much any file size you could imagine, you can upload your HD videos and photos to your hearts content. 

You can add as many Download Blocks as you would like. Your files should continue to upload in the background (even if you lock your phone).  

Click here to see what type of files the Download Block supports.

🌟  Same as any other apps running on iOS, the system might decide to kill the app to release memory if your iOS device is running out of space. This can happen especially with older iOS devices.