Yes, but you could be like the customer that we had. She had bought a direct fit catalytic converter on line and had a friend put it on but it didn't fix her check engine light and she came to us to fix it. What we found was that the converter was flawed in the manufacturing process. Where the O2 sensor goes there was excessive weld built up inside the converter and the O2 sensor would not screw in without breaking the end off of the sensor which her friend installer had done. We now faced the issue of how to fix it. If it had been one of our converters we would have sent it back as defective, would have not broken the O2 sensor, and would have gotten another one and never have installed this one. She couldn't get the seller on line to warranty it but I did finally talk to the manufacturer and they said they would if we could get it to them. However, the solution we finally came up with was to go inside the O2 bung and grind the weld down enough to allow the O2 to fit. However, on top of the money she spent on the converter she now had to pay us about $250-$300 for an O2 sensor, tool to remove the weld, and labor. If we had not been able to do this the converter would have had to been removed, packaged up, shipped to the manufacturer, and a return converter shipped back. She would have had the shipping costs and probably been without the car 10-14 days and would have still had a similar bill from us. While some things can be purchased on line it is absolutely dumb to do so in some circumstances.