This 1.75mm filament run out sensor unit is design for detect whether your printing is run out of filament. During printing if the unit detected that there is out of filament it will send a signal to the main board. With correct firmware settings the printing will paused untill the operator reload the filament and resume the printing. This Filament breakage sensor save your filaments when a strike occures. Its cover is made from Aluminum material, red surface treatment, looks beautiful.