This is an air relief valve o-ring and also a drain pipe o-ring for Hayward Pro Series Plus Filters Models S311SX/S311SXV, S360SX, Pro Series Models S210S, S244S, S310S Sand Filters and MicroClear Vertical Grid DE Filters.
This Hayward part is manufactured by a Poolweb partner to meet or exceed original manufacturer specifications. This item is fully compatible and interchangeable with Hayward part # SX200Z5.
