Pentair 86006900 Upper and Lower Bulkhead O-ring Replacement Pool/Spa Filter 2-331-RPM upper and lower bulkhead o-ring replacement Fits Pentair Clean & Clear Plus pool and spa filters Also fits Pentair FNS fiberglass and FNS Plus vertical grid pool/spa D.E. filters Compatible with Pentair Quad, Nautilus Plus Stainless Steel pool and spa D.E. filters Measures 2-3/4-inch length by 1/4-inch height by 2-3/4-inch width