23.5 mm and the 300SEL (Not 6.3! ) bar is 24.5 mm .

W108 parts #108 323 07 65 and # 108 323 02 65 = 23.5 mm

W109 #323 04 65 #109 323 07 65 = 24.5mm

6.3's have a 23.5 bar # 108 323 04 65
All bars have a part number stamped into them on one end but you have to really look hard to find it.

Bore diameter for the bushes : 23.5 mm bar is 22mm -0.5 mm
and for the 24.5 mm is 23mm -0.5