Terms — carriers, pattern, wires per band, PPI
How the OD stacks up — a 4.9 Fr example
A braided tube OD is the sum of liner, wire, jacket and the resin that fills between wires. From a real inquiry: PTFE liner 0.025 + wire 0.025 + jacket 0.012 + resin fill in the braid 0.02 mm. That wall of about 0.082 mm sits on both sides, so OD is ID plus about 0.16 mm. Add a 0.025 mm marker band and that zone grows again.
If OD is fixed at 4.9 Fr (1.63 mm) you cannot add 0.06 mm and drift to 5.07 Fr. What you can adjust is marker-band thickness, braid pattern (1×1 → 2-wire etc.) and wire size. In reflow the FEP heat shrink sets the jacket thickness, so we re-check against final OD.
Liner — is PTFE always needed?
If a guidewire passes through the shaft, a PTFE (or UHMWPE) liner is the default. PI braided tubing where bore friction does not matter can be PI + wire + PI without PTFE. Coil tubing often has a TPU inner layer. “How many layers?” is really asking whether that inner layer exists.
Kink and length
Write kink spec as a radius: “no kink down to 10R”. 10R is not a demanding value from a manufacturing view. Length can differ between prototype and production — for coil tubing, say, 1,400 mm prototype and 2,100 mm production. Telling us the equipment limit up front avoids a second quotation.