A sleeve or case for a mobile device, such as a smartphone or tablet or other types of hand-held device or mobile smart device, has a sleeve part for at least partially enclosing the mobile device and an input device arranged in the sleeve part for controlling the mobile device which can be received in the sleeve part. The input device includes a movable control element and a magnetorheological brake. Any movement of the control element can be selectively damped by way of the magnetorheological brake.

The present invention relates to the technical field of electric tools, and discloses a rotatable fixed structure and a rolling wheel switch structure. The rotatable fixed structure and a rolling wheel switch structure includes a rotating support frame and handle shells, where a rotating main body is clamped inside the rotating support frame, and a connecting member, a screw assembly, a rubber plug and a rotating base are arranged on one side of the rotating main body. The structure of the present invention is reasonable. With the screw assembly, the rotating main body can be connected to the rotating support frame, and the whole device can be conveniently rotated manually through the rotating support frame.