A spool (1) for use with a swimming pool cover or with a shade cover. The spool (1) has a roller assembly (4), and a cover (not shown) may be wound onto the roller assembly (4) or unwound from the assembly (4). The roller assembly (4) has a pre-tensioned rubber strip (22) that when viewed in transverse cross-section is substantially rectangular in shape and two opposing sides of the rectangle are notched. This strip (22) is tensioned when the cover is unwound from the spool (1) and a locking mechanism retains the cover in a desired unwound position against the tension of the rubber strip (22).
