I've had two of their mufflers on the boat. One smallish one on the generator and one large one on the main engine. I've replaced the small generator one already and had an issue with that needing to be replaced again; a second time. Feeling something was not right I contacted Centek. I was in Panama, Central America when I first contacted them and they promptly sent me to one of their engineers; Bert Browning. He was prompt and courteous. He told me that the mufflers were guaranteed 5 years (I didn't know that) and that when I could get the unit sent to them they would replace it. I had planned on returning to the states during the holidays so I would do it then.
In the states I again emailed Bert but for some reason I didn't get a reply. I called Centek and was promptly informed of the process of how to return it and get the new one. They even believed enough in their product to cover the cost of shipping for return. There is a company that believes in their product and in keeping a customer.
When Bert returned to work he emailed me about the cause of the issue. They've identified it as too hot. I had lost an impeller in the generator. The unit was running without water in the exhaust for a couple of minutes before I was able to shut it down.
The muffler works well, the company is great, and the people treat their customers as an important part of their success. I have bought the product a second time. ( I needed to a third time and didn't replace it with a Centek). I had a SS copy made in NZ. However, the only reason it's listed as a B is I never had any warning in the product info and in this era of special materials I think the product should stand up to Diesel exhaust for say 5-10 minutes without any failure.
A few years after the first replacement I was having the same issue. Salt deposits on the outside of the muffler. I have had enough screwing around with this. I took the unit to my SS shop and he duplicated the thing for a couple hundred bucks. No more salt leaks. I hope this lasts longer. At this point in time the SS box is about 3 years old and still looking like new. Centek Grade B.