Ah thanks a lot @Willem for the photos, now I can see better
And thanks to both of you for the explanations.
So they are adhesive but you CAN take them off without harming the tile, correct?
I was wondering if this could be something I am interested in, but I am not sure.
I like touching the tiles while playing but I can see that tiles get used and scratched and roughened.
I just bought a new (unused) C1 base game because our tiles show white sign of being worn.
This is why this threat caused my attention, but I cannot imagine playing with sleeves, I guess.
I have to think about it
But thanks for the quick reply