Tank Magnets are used in conjunction with conventional filter systems. When used properly as a backup to a filter system, they help trap small ferrous particles that may be missed by the filtration system. Standard Features - TM Series: .39 inch diameter 5 inch long steel support rod Doughnut shaped ceramic magnets Use with PM-250 plug (2.50 inch NPT) Standard Features - HDM Series: .62 inch diameter 5 inch long steel support rod Doughnut shaped ceramic magnets Use with PM-250HD plug (2.50 inch NPT) Standard Features - SL Series: Aluminum housing .39 inch diameter 5 inch long steel support rod .62 inch diameter housing Use with PM-125 plug (1.25 inch NPT) Standard Features - SLX Series: Aluminum housing .62 inch diameter 5 inch long steel support rod .62 inch diameter housing Use with PM-125X plug (1.25 inch NPT) Standard Features -- Magnetic Plugs: Steel body Ceramic magnet Permanent magnet fastened to plug body