CMD563368 800mA Ceramic Cartridge Fuse, 5 x 20mm, Speed F. Miniature ceramic cartridge fuses which are fast acting (F) and are ideal for providing protection to devices or internal circuits from short circuits and overcurrent. They are deliberately weaker components which, when too much current is drawn, will blow. Once the fuse has blown it will need replacing in order to make the circuit complete and allow the flow of current.
Fuses are less expensive and react faster than a circuit breaker. However circuit breakers can be reset after they trip but a fuse will have to be replaced once it blows.