There are dozens of these Chinese built e-bikes being imported - all are exactly the same - just with different decals or logos. Most are built in the same factory and imported in bulk - then seperately branded by each importer. For the most part, these are very low quality e-bikes - and I'm sure the specs are highly overstated. 40 miles with a 48V/12AH SLA battery??? I doubt that!
I guess for the price, it's not a bad deal. But you get what you pay for - so don't be surprised if the controller craps out or if something breaks. Where are you going to get back-up or replacement parts? Does the seller provided support? These would be my big concerns...