Pentair 154412 2-Inch Internal Bulkhead Locknut Replacement Pool and Spa Sand Filter Internal bulkhead locknut replacement Fits Pentair Triton II and C-3 fiberglass pool and spa filter models TR100C, TR140C Also fits Pentair Nautilus, FNS, SM & SMBW 4000 series sand filter model 4060 Measures 2-inch