The rating for the USB is 3.1A x 2 at 5V when one device is inserted, then it divides to split the output when a device is inserted in each USB socket.
3.1A is available across 2 x USB outlets on the left and 3.1A available across 2 x USB outlets on the right.
for further info, head to the manufacturers website by clicking the link below
http://www.gsme.com.au/products/puma-integrated-usbs/puusb4g