How hard is it to spot a new commercial compressor versus an old one? The answer is, it really depends on what you're looking at. For many people, identifying the age and quality of a particular compressor is nearly impossible, because it all comes down to the components inside. Today, there are three main categories of commercial compressors available for sale: new, rebuilt and remanufactured. Knowing the difference between these three products will determine how good of a deal you get on your next buy.