Silicone socks for hotend that will help keep it clean. That's not all. This shoe has other important advantages. One is maintaining the stability of heat during printing. Especially when you are printing from a PLA blown over and around the nozzle his 3d printing.
The sleeve is simply attached from the lower side to hotend and to hotend warms up, adheres to it.
The package contains 3 pieces. The sleeve will not last forever and needs to be replaced once in a while.