I put a set of SS lines on my E53 and flushed and refilled with Dot 5.1 synthetic brake fluid. I suspect the construction has a plastic overwrap over a SS outer sheath with a teflon hose center. Aviation brake hoses made these days seem to have a similar construction with a teflon hose center.

The pedal feel was noticeably firmer after the process.

I felt the 100K mile OE rubber hoses didn't owe me anything and I was going to flush the fluid anyway.

Mike

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Mike
Dallas, TX & Appleton, WI
2003 E53 4.4i Pearl Beige
2003 E46 330Xi Monaco Blue
2007 E90 335Xi Black Sapphire Metallic
2011 F25 X3 28i Black Sapphire Metallic