Keeps Roomba on track

Anyone who has a Roomba, knows the lighthouses, so I will not write it. The Lighthouse functioned as expected and were immediately recognized by the Roomba for the first tour. They are very sturdy, but the batteries should last for me only about 5-6 months, so I switched to batteries.

Unlike as in the Lighthouseses that are supplied with the Roomba, here no batteries are included. Therefore, whatever be ordered with it!