A hose with a PTFE inner tube inside a stainless steel braid - ours is AN6 with a black nylon cover over the braid. PTFE is chemically inert and essentially impermeable, which makes it the choice for aggressive fuels and anywhere permeation through the hose wall matters.

For E85, methanol and race fuels, for high-pressure fuel injection, and where fuel smell through the hose wall is unacceptable - PTFE does not permeate the way rubber does. It is also better for long-term storage, since it does not degrade with age or ethanol content.

Bare stainless braid is abrasive and will saw through anything it rests against - a painted panel, a wiring loom, a brake line. The nylon cover protects surrounding components, is far kinder on your hands when routing, and looks considerably tidier in a finished engine bay.

AN6 hose ends designed specifically for PTFE. The olive and collet arrangement differs from rubber-lined AN hose, and using the wrong ends is a common and expensive mistake - the joint will leak or let go. Check your fittings are PTFE-specific before you start assembling.

Wrap the cut area tightly in tape, cut through the tape with a sharp cut-off wheel or proper hose shears, then remove the tape. That stops the braid fraying. Take care not to crush or distort the PTFE liner as you cut - a deformed liner will not seal in the fitting.

No, noticeably less. PTFE has a larger minimum bend radius and does not flex as freely, so routing needs more planning and gentler sweeps. Do not force it round a tight corner near a fitting - use an angled hose end instead, which is what they exist for.