This is a Aquarium Air Pipe Nipple Connector. To connect two pipes. The outer diameter of the connector is 5mm. Use hard printing filaments for 3d print, like ABS or PET plastic. I used ABS and PET pastic to print it. I found ABS plastic materials are work best. You can try other materials too. But don't use britle materials.

Single and mltiple 3d printable models are uploaded. Base supporting material added for the multiple printing model to adher to the print base. Break supporting materials after 3d print.

Custom size and design possible, please contact with me for more details.

Best Regards,Mahbub