The Creality Extruder for CFS Printing 3D Printer is a high-quality extruder assembly designed specifically for the k1 Series printer. Creality brand users can trust in the durability and reliability of this product. The extruder is compatible with 1.75mm filament diameter, ensuring smooth and precise printing results. Creality is a well-known brand in the 3D printer industry, making this extruder a dependable choice for those looking to enhance their printing experience. I bought this in the CFS upgrade kit. Then decided on aCFS-c. So I never used it. Just been sitting in my parts drawer.