Simple 4mm PTFE tube coupler

thingiverse

Simple coupler for PTFE tubes with an outer diameter of 4 mm. One side of the coupler is flat, so you can fix it on a flat surface using eg. double-sided adhesive tape. Print it in a standing position, use brim if needed. The inner diameter on the model is 4,1 mm, so if you expect shrinking, upscale the model a bit, but be careful, the tubes should have a tight fit on both sides.