If you are speaking of the Dorman ones that are like the Flexx Boots; both have the ability to stetch over the Cans on the Axles.
I believe they must be made of some good stuff to be able to do that.

If you plan to use a Hydraulic Press and Press apart your Axles you have a choice of the Stock Boots or the Flexx Type Boots.
If you intend to stretch them over the Cans you cannot use the Stock Boots.

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84 300D, 82 Volvo 244Gl Diesel