yup you are right i guess, so far both fronts when they perished did so on larger end of bellows that flex more, those were the oems on car for about 10years....replaced one side with febi brand and the other can't remember....to be frank the spraying of silicon on em has mean't they are spotless,no grime or grit seems to have collected on em...will keep an eye out on the small end of one of them where it has cracked superficially....

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E53 X5 3.0d SUV prod.date 11/2004 eng.variant M57N Europe Right hand drive N