Voker Holding Tank Vent Filter - Direct Replacement for Sealand/Sanigard/Dometic OEM Filters (1-1/2") Connection size is a large 1.5 Nat Pipe Thread MNPT. Just larger than the diameter of a golf ball Please double check your connection size and old filter part number to insure a proper fit. A high-density carbon bed & air diffusing retaining barriers yield unrivaled air quality & flow Our minimalistic design promotes ease of use and reliability Made with pride in the USA