A delivery system for a drug or bioactive agent includes an implantable pump and a delivery conduit that may be implanted in an organ or other tissue of a subject. The damper prevents unwanted unwinding of hose pipe from the drum due to inertia in the latter. Six or more ribs are provided as the plural ribs and an angle \u03b8 formed between extension directions of a respective pair of adjoining ribs is less than 90\xb0. The aim of the invention is to provide a device which enables the level or the density of a filling material in a container to be measured reliably.