Both gears are made of steel , which can prevent from rusting so that it can work for long time. The hardened steel extruder gear assembly is an internal component of the hardened steel extruder unit. It comprises a driven gear and an active gear that work together to feed filament into the hotend. Built with heavy-duty materials, the extruder gear assembly is designed for long-lasting performance. However, if abrasion or clogging occurs due to extended use, the extruder gear assembly can be easily replaced. Thanks to its hardened steel gears, the extruder unit is capable of printing with tough engineering filaments like carbon fiber nylon and glass fiber nylon. The P1P stainless steel extruder can be upgraded to a hardened steel extruder by just replacing the extruder gear assembly. The extruder gear are made of stainless steel, if you print tough engineering filaments like carbon fiber nylon and glass fiber nylon, than it will get abrasion,so in this case, we suggest you to use this handen steel one. Reduction Ratio:9 : 53 Supported Filament Diameter:1.75 mm Supported Filaments:PET-CF, PAHT-CF, PA6-CF, PLA-CF, PETG-CF, PLA, PETG, ABS, ASA, PC, TPU For P1P owner Colour:Photo Color Material:Hardened Steel Package Contents: 1 x 3D Printer Gear Assembly Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.