The Harbor Freight Pittsburgh is a 3 CFM Two Stage HVAC Vacuum Pump.
It is rated to pull a vacuum to 22.5 microns.
It will work with most any refrigerant, R134A and R12/R22.
Vacuum pumps are often are high priced units and can cost upwards of $500-$1000 dollars.
At less than $200 dollars this unit from Harbor Freight makes it more affordable for home DIY or part time HVAC technicians.
It could also be used on a vehicles cooling system but I only used it with a home air conditioning unit.
I had no problem evacuating the system, it pulled it down the unit I tested it on relatively quickly.
I let this sit there and run for a good hour since it was a system broken open because they stole the copper from it.
I did pull it for an hour, I had no problems with it maintained its vacuum throughout the entire time.
It seems to start a little noisy and I think they mentioned it in the manual and after a couple minutes after it draws down it quiets up.
It is quiet now and running which is great.
I would recommend it for those working on there own systems and need a cheap unit to work with.
It could be used in a professional setting or as a backup although there are better units although more costly.
I am still testing the unit out and will update if anything changes.
As always be sure to read the reviews on forums or elsewhere to be sure a unit is a good fit for you.