A medical balloon (14) has a strengthening sleeve (50) formed of circumferential fibres (52) and longitudinal fibres (54). The circumferential fibres (52) have a greater thickness than the longitudinal fibres (54) and preferably have a greater cross-sectional area or volume. In one embodiment, the circumferential fibres (52) are twice as thick as the longitudinal fibres (54). The use of thinner longitudinal fibres reduces the thickness of the strengthening sleeve (50) and as a result enables a thinner balloon wall, whilst still retaining the circumferential strength of the balloon (14). Reduced balloon wall thickness improves the foldability and wrappability of the balloon for deployment purposes, and therefore provides a balloon with a smaller diameter for deployment purposes, with improved trackability through a patient's vasculature.
