Parking space for 7-pin electric plug. The lower, narrower area of the plug holder parks form-closed the 7-pin electric plug. Parking space for 13-pin electric plug. The upper, wider area of the plug holder parks form-closed the 13-pin electric plug. At the same time parking space for Soft-Ball. When driving, the plug holder serves as a parking space for the cover ( Soft-Ball) of your towbar cover. Max. diameter electric plug: 13-pin 41,5mm, 7-pin 36mm.