Markel PTFE tubing is commonly used as Bowden tubing for 3D printers and comes in English and Metric sizes.
What is a Bowden feed?
In the realm of 3D printing there are two separate ways to get your filament to the hot end. One is right out of a motor with a toothed gear on it, the other is to place the motor somewhere else. The secondary option uses this tube. The motor can be located elsewhere and the filament can be run through the Bowden tube to the hot end.
Markel PTFE Bowden tubing can be used for bowden systems and is compatible with various diameter filaments. The tubing fits to the threaded bowden coupler which can be screwed to the Full Metal Hotend Round Mount.