Voker's VKR-HTVF-150 Holding Tank Vent Filter (1-1/2" MNPT connection) offers an affordable replacement filter cartridge for marine holding tank applications. This filter effectively eliminates holding tank odors expelled through your vessel's holding tank vent. Please note, this item features the large 1.5” Male National Pipe Thread (MNPT) connections. The diameter of the threaded connections is slightly larger than the diameter of a golf ball. This is NOT the 3/4" Garden Hose Thread (5/8" hose) connection filter. The VKR-HTVF-150 is a direct replacement for the old style Sanigard 309310003/309310004 (Dometic) and Trionic TF150 1-1/2" vent hose filters. Please check your part numbers and connection/fitting size to insure a proper fit. Note, to insure against air leaks the ends of this filter are fixed and not removable