You'd be forgiven if you forgot what the Surface Hub is. After all, Microsoft announced it the same day as its futuristic HoloLens headset -- arguably the more interesting of the two products. Even so, though, the Hub is a compelling device in its own right: a big pen display designed for conference rooms, making it easier for employees to brainstorm, even if some people are tuning in remotely. We took one for a brief spin back in January, but at the time it was unclear when it would be available or how much it would cost. Today, Microsoft clarified that the 4K, 84-inch version we tried will cost $19,999 and go on sale in July, right around the time Windows 10 comes out. In addition, there will be a smaller, 55-inch version available for a much lower price of $6,999. (For the money, you get 1080p resolution on that one, which is just fine considering how relatively small the screen is.) Both should ship in early September.