Don't be surprised if your AC O-ring looks fine but your air-conditioner is leaking. Seals naturally wear out over time and though you may think nothing's wrong with your O-ring, it could've flattened out or turned brittle. The tiniest opening could let refrigerant escape, so you must replace your old O-ring immediately. And to make sure your replacement part lasts longer than your factory seal, go for something that's trusted by motorists nationwide: the Largo Filters A/C O-Ring.It is common for O-rings to leak in AC systems, especially those that are old since they get hard over time. If you very rarely use your AC, then that could be another factor why your O-ring failed 'cause refrigerant lubricates the O-ring. Good thing you can always get a replacement seal from Largo Filters. The company has been supplying high-quality aftermarket parts to drivers and auto repair shops for a long time. Their products comply with the highest industry standards and meet or exceed OE specs. There are many other automotive seal manufacturers out there but if you really want to invest in a heavy-duty O-ring that'll give you peace of mind on the road for years, you should go for Largo.Before installing a replacement seal from Largo though, make sure your O-ring is indeed the part that leaks. There are many ways to do this. One is through the use of a UV dye that instantly shows you the location of the leak. But if you want to save money, you can make a solution of water and liquid dish detergent then spray it on your AC's O-ring and hose. Turn on the AC and see where the bubbles are coming from. If you see them appearing on the fitting area, then your O-ring indeed needs replacing.