... : 35mm,50mm 3.High effective 4"-12.5" Hydroponics Activated Carbon Ventilation Filter *Carbon layer thickness: 35mm, 50mm*Color available: Black, Grey 1. Working ... fan, Grow tent, Carbon filter, Light reflector, Electronic Ballast, Heavy duty hanger, Flexible duct... Rope Ratchet Filter Hanger 4"-12.5" Hydroponics Activated Carbon Ventilation Filter