this is my attempt at the big tree tech filament joiner, i dont know if it will work but im going to try so i figured id share so others could give it a shot. ive seen others on thingiverse but none made like this an this one i modeled to be as close as i could to the one big tree tech offers but i made it thicker since its being made from plastic while the big tree tech one is aluminum. i made 2 different versions one that is completely lined with a ptfe tube or one with just the back half lined with ptfe tube and the front is just model into the part, if u decide to go that way, u might want to print the block in petg or abs if u plan to use it with pla. if ur going to try to join petg or abs u would probably need to go with the fully lined ptfe tube. it does require u to cut the ptfe tube to the shape need an also splitting it down the middle. i used the block its self to hold the ptfe tube while i slide a utility blade through the middle an it came out perfect on my first attempt.