PTFE low-density cords are used as cable fillers.
These are soft materials used to fill the gaps in the cable. They easily deform themselves and help binding the cable while keeping a round section.
They also are available as films.
*Prices are pre-tax. They exclude delivery charges and customs duties and do not include additional charges for installation or activation options. Prices are indicative only and may vary by country, with changes to the cost of raw materials and exchange rates.