These are spare parts for Arkal 50mm and 80mm plastic Filters.
See the diagram to make sure this is the replacement part you are interested in.
#11. 50mm Spine Tightening Nut (Grey)
#14. 50mm Filter Clamp 304 St/St (also suitable for Arkal 80mm filters)
#15. 50mm Hydraulic Seal filter Cover (also suitable for Arkal 80mm filters)
#16. 50mm and 80mm Filter Cover/Bowl
NOTE: Parts may take up to 2 weeks to supply