Abstract: Apparatus comprising an inner cylinder and an outer cylinder which are telescoped with respect to one another to define between them an annular treatment chamber in which materials, such as textiles, are treated with a fluid medium. The ends of the annular chamber are closed by radial flanges on one of the cylinders, and clearances are sealed by pressurized seals. Material to be treated is wound onto the inner cylinder, and fluid medium is circulated through the chamber while one cylinder is rotated and the other remains stationary. At the conclusion of treatment, one of the cylinders is moved axially with respect to the other so as to expose the inner cylinder for unloading and reloading. Novel T-shaped seals of rubberlike material are mounted within annular grooves in the cylinder flanges, with the head of the T forming a diaphragm and the leg of the T projecting toward the other cylinder.