Antec's recently-launched P280 and Eleven Hundred cases feature two USB 3.0 front-panel ports apart from two USB 2.0 ports. The USB 3.0 ports connect to the motherboard via standard 2-port USB 3.0 front-panel header. The front-panel header designs of USB 3.0 and USB 2.0/1.1 are different, and so for those with motherboards that lack USB 3.0 front-panel headers, the two USB 3.0 ports are rendered useless.
Some of Antec's competitors have bundled USB 3.0 to USB 2.0 front-panel adapters that allow you to connect USB 3.0 front-panel ports to USB 2.0 headers, so at least they could function in 2.0/1.1 modes. This caused Antec's customers to request similar adapters from Antec. The company more than obliged, and in fact is giving those adapters away to existing customers of P280 and Eleven Hundred for free. All existing customers have to do is write to email@example.com with their shipping address and a proof of ownership of P280/Eleven Hundred. It's likely that Antec will begin bundling the adapter with all the P280 and Eleven Hundred cases it will ship hereon.