I don't know the diameter, but from the picture I saw, it dwarfs the 500E sway bar. Probably unnecessary, and it would cost two to three times what a Sportline sway bar costs.

Did you use the MB Springs and shocks/struts or did you go Bilstein/Eibach? The latter is less expensive by a bit.

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1994 E500 199/Gray 82k
84 300D (Salty) Orient Red/Palomino 141k
88 300CE (Ersatzhammer) 904/Java 163k -- Turbo Technics twin turbo kit, AMG Gen I body kit, Sportline steering box and steering wheel, Sportline/Eibach /Bilstein Sport/500E suspension, Quaife LSD in 210 mm diff case, Silver Arrow brakes.
88 300CE Brabus 3.6 199 on Black 44k