Cabin filters are a important part of modern day cars ventilation systems especially the A/C. They simply filter out all the dirt & dust & harmful pollutants from the air entering the cabin of the car. It has become standard procedure to check/ replace the cabin filter as part of servicing modern cars from about 2000 on, it is mostly a simple procedure to check/ replace these filters but I constantly come across new customers cars that haven't been checked/replaced for a very long time. Your cars A/C especially can't operate properly with filters as blocked as the ones in these photos from customers cars. This happens due to a number of reasons..., slack mechanics not doing their job properly, fixed price services where you don't get what you don't pay for as much as you don't get what you pay for as well!