Removal (yes, getting it not quite right can be like extracting a plunger): I find that, if it's gone too high, it helps to pinch the base between thumb and middle finger, pull down slightly while bearing down, that gives me the chance to reach slightly higher and pinch just above the base, again with thum and middle finger, and squeeze while rotating. It sort of spirals down, and then I remove it - oh, I can't remember now whether I take the front edge of the rim out first or the back edge, but it's a sort of rocking movement, rather than trying to get the whole rim out in one go. Sounds complicated, but you do get the knack eventually. I never managed to follow their advice to reach up the side and break the suction at the rim.