Sig P229 9mm Threaded Barrel. This barrel fits only older style P229's and P228's. If your P229 is made in Exeter, NH and shipped with 15rd magazines (MAG-229-9-15-E2) or the newer 229-1 10rd mags (MAG-229-9-10-E2) then this barrel will not fit. If your P229 was made in Germany or came with a 13rd magazine or an older style 10rd magazine, it will work. Finally, it will not work on P229's in California that have a loaded chamber indicator.
Note that it is not uncommon for barrels to need fitting. We recommend having a gunsmith perform this.