They come with a gasket. Smear some blue/copper rtv on both sides tho and let it go off for 10 mins before fitting, scrape all gaskets off with a Stanley blade and clean up to shiney with some emery cloth/tape
Do a search of my last few threads one was on water pump and the eBay supplier, click4carparts I think ??? They were cheap as fk and it was a QH part which was quality
There are 2 types tho, yours is different to the one I had as its a non intercooler