This package contains four PC4-M10 Straight-Thru Bowden Fittings.
This is the fitting you need for the Hotend side of the CR-10 (version 1 and 2) Bowden tube.
These fittings have a 4.1mm inner diameter, to allow the tube to pass all the way through.
Thread pitch: 0.9mm
For 1.75mm filaments.