What is the difference between a 3kVA Tower and Rack uninterruptible power supply?

A 3kVA rack mount UPS is designed for installation inside a server cabinet. A Tower unit is a free standing unit that normally sits on the floor. A combination Rack/Tower or Tower/Rack 3kVA UPS is dual form factor UPS designed to be installed as a 19inch rack mount UPS or a floor standing tower.