Order one each for lanes 4 through 8 if your track has more than 3 lanes. Or if you would like to have some extra sensors as spares. The cable length is 10 feet. This length can be altered if needed, but you must purchase the additional $4.00 charge per each cable you need altered. These charges are also listed in this section under Optional Items. These stop sensors are used only with the DTX000 Product line and are not needed with the TURBO.