Abstract: A hearing aid, in particular a behind-the-ear hearing aid, comprising a first unit (1) that includes an amplifier (4), a hook (3) formed with a duct (16) and a space (8). A second unit (2) includes an electro-acoustic transducer (12). The second unit is intended to be worn in the ear. A tubular element (15) for the mechanical connection of the two units accommodates connecting means (14) for electrically coupling the transducer (12) to the amplifier (4). The element (15) is axially slidable inside the duct. This enables the hearing aid to be adapted to the size of the ear of the person wearing the hearing aid. The connecting means (14) is long enough so that even for a big ear, the electrical connection is still intact or can be made. When the hearing aid is adapted to a smaller ear, the connecting means (14) is then too long but the space (8) takes up the excess length of the connecting means.

Abstract: A tube coupling with snap action for quick interfitting of tubes or tubular articles.

Abstract: A tennis racket comprising a frame having two spaced apart peripheral rows of threading openings for two spaced apart string cord layers, and an intermediate flexible layer in at least the central interspace area between said two string cord layers to interconnect said two string cord layers.

Abstract: An ever open link-chain, i.e. a link-chain having links which are readily to be mounted or dismounted manually without deformation but cannot get detached of themselves without manual intervention.