They're available in several different sizes.
Source
From the announcement:
Pre Orders now being taken
Shipping will begin November 15, 2013
If you will be attending Warmachine Weekend in November, I can deliver your bases to you as I will be attending.
Include a note that you will be attending WMW when you order or send me an email to dragonforge@gmail.com
Also, All Pre Orders will include an extra FREE Surprise!
(No, I wont tell you wihat it is it wouldn't be a surprise)