The FSL flange type originally was developed to fit gas springs with a lower C-groove and consists of two halves with a lock ring between.
The FSL flange can be used for both upright and upside-down installations.
The FSL flange can also be used on gas springs with a lower U-groove by using the additional FSL adapter ring.
The FSL adapter ring is ordered separately and is to replace the standard lock ring included in the FSL flange.