The rubber from the circle pad on my 3DS fell off, the robber has some tears on it so it will not stay one even if I put it back. I tried to use it with like that, but it was too slippery and my finger started to hurt after an hour of play session.
Probably I could just leave to be like that, but I thought since there's replacement ones sold even if those are not original I will be better of with them then the original without its rubber.