No such thing. posted by BlackholeZ on April 15, 2016 at 07:34 PM
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to cover the central circle of light emanating from the bulb. The purpose is to defuse the beam coming out of the fog light...not concentrate it. Like Bernie notes, it defeats the purpose of a fog light. OP is building a driving light were his fogs used to be... and yes I would think it needs a fence to keep the light out of eyes of on-coming drivers.