These pneumatic fittings have a brass metal body which is designed to provide a simple and cost-effective way of inserting bowden tubing directly into your aluminium components.
The couplings are designed to take PTFE tubing with an outer diameter of a 1/8" (3.18mm) for 1.75mm filament, and 1/4" (6.35mm) for 3mm filament. Tubing inner diameter will vary according to its filament suitability.
The brass inserts push into an 0.528 Inch (8mm) hole 0.181 (6mm) Inches deep. E3D apologises for the use of imperial units.
These fittings are used in both types of the 1.75mm V6 hotends, the 3.0mm Bowden V6 hotend, and the Cyclops/Chimera/Kraken hotends. However there are plenty of other applications ready to be discovered!