Abstract: A connecting device has an attachment head and a clamping device for connecting horizontal or diagonal scaffolding elements to perforated disks of vertical post elements. The attachment head has a bearing surface on one side by which it is supported on the pipe of the post element. On the same side a horizontal slit is present, corresponding at least to the thickness of the perforated disks. The slit divides the bearing surface into two sub-surfaces. A feature is provided on the side opposite the bearing surface for welding on a pipe. The overall height of the attachment head on the side by which feature the attachment head is supported on the pipe is at least 68 millimeters. The top surface and the bottom surface of the attachment head taper continuously from the bearing surface to the feature for welding on the pipe.