A cylinder for handling continuous lengths of web material comprises a rotatably mounted tubular casing, a spindle extending from end to end of the casing and arranged to be stationary in relation to rotation of said casing and having an external diameter less than the diameter of an inner face of the tubular casing, at least one support bearing which is symmetrical in relation to the middle of the cylinder and coaxial to the cylinder, the bearing bridging over an annular space existing between the casing and the spindle, oil at least partly filling the annular space, at least one heat exchanger placed in the annular space and surrounding the spindle, mounts fixed to the spindle for locating the heat exchanger thereon, and connection ducts for coolant, at least partly in the form of lengths of flexible hose placed in recesses in the spindle, the connection ducts being adapted to join the heat exchanger with an external coolant supply and return duct.