This small piece of trim is available from smart under several different part numbers as there are a variety of different finishes available.

The silver end caps on the fortwo are notorious for cracking due to the poor way in which they are manufacturered. The arrow below points to a crack that is starting to form.

Try to remove the old ones by twisting them off the stalks. If the caps are split, they will come off very easily. If they are stiff, use a small screwdriver but be careful not to scratch the plastic.

The new ones are fitted by pressing them onto the stalk firmly until you feel a 'click'.