UPDATE: i added another version that has round tubes instead of square. the top or bottom is still square but the rest is round. thats how the one we bought is made so i thought i go back an try to make it just like it. ive not printed these yet to try them but they should be the same as the ones im using now just being round instead of square. thought id update this with them incase someone who wants to try this would rather have the round instead of the square.

so we had a regalo baby or pet gate an it works great when used in door ways but we wanted to use it between our kitchen an dinning room to try to help keep the dogs out of the kitchen while cooking. the gape was to big but just a touch so we used some 2x2 wood to fill the distance an it worked but the tension screws was extended quite a bit an it was as sturdy as id like, worked good enough for the dogs but when the kids was around they would push it loose without even trying so i took some old metal tubes i had from a old shelf i had disassembled an designed up some parts to make the extension. while doing this i found u could buy them but i went ahead an finished it an im glade i did. i dont think the ones u buy could be much sturdier. i made it 150 mm long and the gap between the bars are 75mm give or take a few depending on what size tubing u use. but its mainly for my specific space i needed but i can make them bigger or smaller if someone likes an i may add a few different version so ppl have more options to suit their needs but it also depends on the size of the tube u have. im sure u could use dowel rods if they dont have metal tubes. its not worth doing if it ends up cost more to buy the stuff to make it then the actual part so keep that i mind. i keep alot of old stuff just incase i can use it for something so i have alot of random stuff on hand most would probably have thrown away so if u dont have access to metal tubes the size i used the diameter of one hole is 16.4mm and the other was 15.3 so the tubes was 16.1mm an 15. i gave .3mm of space for clearance an it makes for a nice snug fit that strong enough to hold them in place while not being so tight its hard to pull apart if needed. for any request on changes to the length or size of the holes let me know in the comments an i'll make the changes as soon as i notice. if i dont notice or respond try sending a private msg.