Abstract: An extrusion die for foam sheet including a die body defining a manifold for conducting a split stream of heated and pressurized foamable thermoplastic melt through separate distribution channels to a die terminus. A pair of mating die lips are arranged on opposed sides of the melt and are constructed to adjustably slide toward and away from each other to vary the flow of a melt. The lips are each mounted to slide along an axis which is tilted rearwardly at an acute angle relative to an orthogonal to the sheet being formed. The mandrel is configured and adapted for quick withdrawal and replacement from an end of the die through a passageway extending through the die transverse to the direction of extrusion of a sheet.