Electrical stimulation system

A mounting sleeve 4 for a medical device comprises an elongate flexible sheet 40 having an interior face (41; fig 13), an exterior face 42, a tail region 43 at a first longitudinal end 46, a head region 45 at a second longitudinal end 47, and a central region 44 between the head and tail regions. The sleeve further comprises a hinge 48 composed of a flexible material and attached at the second longitudinal end of the flexible sheet. The hinge comprises a first surface (414; fig 13) on the same side of the sleeve as the interior face, a second surface 415 on the same side of the sleeve as the exterior face, a sizing fastener (412; fig 13) on the first surface towards a distal end, and a securing fastener 413 on the second surface towards a proximal end. The flexible sheet has a sizing attachment point provided on the exterior face in the tail region and is suitable for releasably mating with the sizing fastener, and a securing attachment point provided on the exterior face in the tail region and suitable for releasably mating with the securing fastener. An electrical stimulation system and kit of parts is also disclosed.