If a part is temporarily unavailable, you could substitute it with these parts:
Quality Parking heater glow plug for Mercedes R-Class R 63 AMG 4-matic 510 hp Petrol
Wide selection of new parking heater glow plug for Mercedes W251 R63AMG 4-matic (251.077, 251.177) Petrol 510 hp, priced from £166.48 to £466.72. Choose from 1 trusted manufacturers.
Auxiliary heater glow plug for MERCEDES-BENZ R-Class models
R 320 CDI 4-matic (251.022, 251.122) OM 642.950
R 350 CDI 4-matic (251.023, 251.123) OM 642.872
R 350 4-matic (251.065, 251.165) M 272.967
R 280 CDI 4-matic (251.020) OM 642.950
R 500 4-matic (251.075, 251.175) M 113.960
R 350 CDI 4-matic (251.022, 251.122) OM 642.950
R 280 CDI (251.121, 251.026, 251.126) OM 642.950
R 320 CDI 4-matic (251.125) OM 642.950
R 300 CDI (251.021, 251.121, 251.026, 251.126) OM 642.872
R 350 (251.056, 251.156) M 272.967