This should fix a common problem people have with the Ender3 where the PTFE tube pops off. it clips around the pressure fitting to hold it tight.
There are 3 different sizes for each side. 1mm 1,5mm 2mm this is because I don't expect them to all be the same you don't need to force it. You just want to stop the fitting from being able to depress.
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Slow print speed is probably better for this 20mm/s works fine.
Designed in Fusion 360
look at my youtube channel I show how I do basic designs.