Manufactured in hardened steel with an protective surface treatment will give you long lifetime and extreme reliability.
The gears come as a set consisting of a Primary drivegear with a M4 setscrew, fits on a 5mm or 8 mm shaft with a flat side as those on Nema17 motors with a planetary gearbox attached. A secondary drivegear with integrated high quality bearings. Add your shaft of your preference below, we have them in two lengths 22 and 25 mm, hardened ground steel.
A Lithium based grease is recommended to use on the gear section and in side the needle bearings for low friction and to avoid wear. A small dab of grease is enough.