The relatively small back light does not actually show the actual width of a BMW, especially when side cases are attached.
This tailor-made 3M film kit reflects the light shining on it which increases the signaling effect considerably. The actual width is immediately visible and the vehicle can be seen from a distance, increasing passive safety enormously. Simple to apply. Made-to-measure for Original BMW cases. The reflective material is black, and thus nearly invisible in daylight. At night however, lights from vehicles behind you brightly reflect.
Kit contains enough material for both bags. Clean the bag lids, peel and stick.