The KPSI 811 permanent vent filter provides a minimum of five years of moisture protection without maintenance. The housing is constructed out of a stainless steel body containing the desiccant, while a Gore-Tex filter plug provides atmospheric reference without letting moisture into the casing. The vent filter is a compact package at 2.75 by 0.75 in. in diameter, making it easier to fit into a tight junction box confine during installation.