Hello
It says on the packaging that it fits the UniversalRotak
36-555. I haven't fitted it yet, but it is exactly the same as the original in the mower. Good luck!

Hello, I think so, I have the Universak Rotak 36-550 version and it plays perfectly. It should be compatible with the whole 500 range whatever happens.
Don't forget to insert a screwdriver to lock the blade when unscrewing and screwing it back in (it's written on the box but it's not very clear...).