Special adapter for mounting the sensor on a metal or other material tank with an existing hole. For tanks using S3 flange, just mount the Gobius C with this adapter. For S5 flanges, pair the Gobius C adapter with the mounting flange code 52.746.10..The adapter is screwed into the existing "Wema & KUS" brackets, 1.25″ SAE 5. The sensor is then mounted on the adapter using the supplied 3M tape.All included: Adapter + 3M tape + o-ring for sealing.