I bought a couple of the circular, convex side mirrors recently. These are to be a Christmas present from my sons and I am under orders not to touch. However, I went into the garage with them to have a sneaky test-fit. A small problem immediately showed itself when trying to release the existing oval mirrors. I undid the centre screw to free the mirror stem from the base arm, slid up the rubber seal and pulled. The stem would only slide up so far and would not come out of the base. I don’t want to pull too hard and break something. Is there something else I need to free or undo in order to separate the two? I notice there is a plastic collar beneath the rubber seal; maybe this has to be prised off?