The most preferred fermentation vessel used by professional brewers is the conical fermenter. Made of stainless steel these fermenters are durable and rustproof. With the ability of dumping the trub out of the bottom via a ball valve these fermenters are "rackless" meaning that they don't need to be rack to a secondary fermenter to age or lager. Being made of metal these fermenters are opaque so light is not an issue during fermentation. The bottoms of the conicals are sloped severely so that all the yeast and trub from the boil kettle will settle at the point of the fermenter. In commercial applications the conical is jacketed with insulation so the temperature will stay constant. In home brewing a racking port is fabricated to the side to allow transfer of the beer with very little trub being picked up.