Filament sensor bracket for Ender 3 S1/S1 Pro. I believe it is compatible with other 3D printers that have 2020 square extrusion on the top of the gantry. You can adjust the position along the X axis (useful if you have more than 2 spools). If you have brass heat inserts, use M3*3*4.5 inserts, but it's not necessary, and an M3 screw should fit like a glove.