Product Description 6PCS Comgrow Printer Hotend Silicone Sock Heater Block Silicone Cover for Ender 3 / Ender 3 Pro / Ender 3 S1 / Ender 5 CR-10 10S S4 S5 Material : Silicone Color : Black Size : 23*23*13 mm/0.9 x 0.9 x 0.5 inch Features It will keep your heater block clean and free from burnt and blackened plastic.They don't just keep the block clean, but also keep heat inside the hotend and off your print.Using Note If your print head temperature is above 250 degrees for a long time, please remove your silicone sleeve.Long-term temperature above 250 degrees will damage the silicone sleeve!