Sold by length - 50mm or 1 Meter increments, 4mm OD x 2mm ID comes in Natural or Blue, if it matters to you please specify the color when ordering.
Hot end Liner - Replacement PTFE liner for the mk style extruder throats. If you overheat your extruder you can ruin your liner, this is an easy fix.
50mm is enough for 2 replacements.
Make sure to cut this flush with a very sharp razor blade. Any gap will cause clogging.
Extension / Bowden - Longer pieces are good for extruder extensions or Bowden systems.