You can keep your block completly clean with a silicone cover, even after using your block for a long period of time.

• Silicone cover will keep your nozzle clean and free of burnt on blackened plastic.
• They offer a huge boost in temperature stability, particularly if you use high airflow cooling around the nozzle to cool the print.
• Made of a heat-resistant, non-stick silicone material. This really helps with sticky materials like Co-Polyesters and filled materials that like to build up on nozzles.
• High-temperature resistance: 280℃. 
• Extend the life of the heater block and extruder by keeping it cleaner.  
• The sock also acts as an insulator for the print head. It will reduce heat up time and help maintain a constant temperature during printing.
• For Printers with E3D V6 exstrudor.
• 20x16x12mm. 
• Package Included: 1x Heater Block Silicone Cover.