- HD 25-1 / HD 25 CII / HD-25 II no. 40178E - Impedance: 70 Ohm - Plug-in connection - Thickness: 27 mm - Diameter (with border / without border): 68.5 / 64 mm - Suitable for left and right side - Includes: 1 Piece - Sennheiser no. 570609 EUR 49.00 - See more - Buy online