The Manufacturer had an Engrish discription, so let TS break it down for you:

Specs:

- Tig Welded Aluminum Tank
- 750 ml Capacity
- Monitor air flow with build-in psi gauge

• Overall Size; 7" X 3.75" X 4"

• Tank Size: 5.25" X 2.5" X 2.5"

- Availible in Siliver/Chrome, Blue and Red

Catch cans are used in a number of ways, from track regulations for vent-to-atmosphere setups, to intercepting fumes before they enter the intake system.  This catch can has a neat vacuum gauge on it, very cool to see how much vacuum your crank case ventilation system is making.  Even better is the gauge will act as a safeguard letting you know if crank case pressure are building up, an indication of a blockage in the system or of a faulty PCV valve.