You can find all the parts of your UM2 on GitHub:
The pulleys you are looking for are 20 teeth 2GT (or GT2) pulleys with an 8mm. bore, - The UM2 uses both single and double ones, ie.:
They are available from many many sources and vary greatly in quality, so if you are replacing them in hopes of getting better performance, you probably want to go with something like misumi or similar, rather than cheap chinese ones from ebay or aliexpress.
You should be fine with the belts you have (unless they are worn)Edited by Guest
I don't want to push - 73 user read this post but nobody can give me any recommendation or tell me some experiences?
Did you check if your pulleys sit centered on the axes on UM2?
What do you do if they are not centered?
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