A geometry connector is a small device that, used along with other similar ones, allows to connect straws and to create geometrical forms.Available straws which exist on the market come in a great variety of diameters – from 3.5mm to 12mm or even 14mm. 3D printed connectors present the benefit of being customizable; they can be printed so that they fit any straw diameter.
Read the full tutorial here : https://wikifab.org/wiki/3D_printed_geometry_connectors