Does anyone have these and do they work on porcelain items do you know?

Does anyone have these and do they work on porcelain items do you know?

They are described as ok to use on most materials and 'crockery'

I have them, no good for little ones though as have to wait for one colour to dry before going over it otherwise they just soak up the ink on the porcelain and get ruined...lesson learned and they're not used as felt tips anymore when doing these sorts of activities!