From the Haas website:
The HRT SP Series gives you the same features and benefits as the standard HRT Series, but the motor is wrapped behind the table to provide a substantially shorter overall length, and help you fit a lot of table into a small work envelope. Note: SP models do not have a through hole. The bore depth is the thickness of the platter.
It has the same working specs of the Haas HRT-210. But is made to take up less table space.
Pneumatic tailstock is also currently available. However it is being listed separately and so it may be sold individually.