To add to the confusion I think GKN was the original supplier for the soft boot and Loebro for the hard boot but now they are the same company and both names are on the boxes!

Back when I did get OE BMW boots they came with the really heavy duty clamp that you would probably have trouble installing with the usual tools.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)