This is a soft semi-clear (translucent or lightly frosted) rubber tubing (hollow) that is easily configured to the space you have. It's able to bend at a sharp angle without kinking or folding.
See Hex Fittings or Ferrules for this soft line.
This soft line equals the following equivalent 1:1 size at each scale.
1/25 scale = 1 3/4"
1/16 scale = 1"
1/12 scale = 13/16"
1/8 scale = 9/16"
Depending on your scale, typical uses are FC/TF 'puke' lines, larger coolant hoses and fuel lines, as well other larger transfer lines.
This soft rubber line is easy to bend and shape to your installation.
Each package contains one coil of .066 x 12" rubber tubing