I bought my stove used and put it into service for the 2003 winter. for 2004 I replaced the cats and rebuilt it with new gasketing, etc. This year I ordered a whole new damper assembly. And while discussinng my needs with customer service, I discovered thaht my stove takes 4 catalysts. 2@1inch and 2@2inch. I have been running it with 1 set of the stove combustor's 1 inch cats since winter of 2004. well I guess I'll buy some new cats and see what it can do.