In my mind, the critical element is 3 part construction. Mine are SS outside, teflon inside and a sheath of Kevlar in between to protect the teflon from small, abrasive contaminants that work their way into the SS mesh and abrade the teflon-a bad thing.
I sourced mine for my 500E from
www.germanautoparts.com ; they're apparently manufactured by a Porsche dealer in California.
Small, but noticeable, improvement
