Much like the fad with magic stickers, (promoted as signal "boosters" and "enhancers") this is a total sham- but I fell for it. Has no discernible effect whatsoever on cell signal, regardless of where placed in vehicle. (tried directly touching it) - Would never buy again. Had no additional benefit in stronger areas, useless in rural dead zones- will probably have to consider a proper signal amplifier system. ($100+)