The air cushion tube is inserted from below the nozzle base and held in position by screwing on the slotted part. This special type of assembly can compensate for slight misalignments of the nozzle base.

The larger outer diameter results in a higher filtration area. The arrangement of the slots ensures a horizontal distribution of the backwash medium. The filter nozzle type C1 is often used in ion exchangers or activated carbon filters.