I'm trying to replace the rear brake hoses on a 1989 420 SEL. The nuts where the hose meets the steel line are on very tight and normal box wrenches are starting to slip especially the 11 MM steel nut on the steel line side.

I hear a flare nut wrench should work but I don't have these wrenches. Should one use a crowfoot flare nut wrench on a 3/8 drive or would a normal flare nut box wrench be better ? Which one should I get?

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1989 420 SEL