The gains are small but significant considering I live and work in a rural area wheres there are more cows and horses than than there are cell towers this small inexpensive antenna makes a difference ,I have far less dropped calls. While driving home I  will travel from 4g with 5 bars to 2g with two bars and it will fluctuate from 1 bar at 2g to three every little fluctuation would drop my call. However since installing this on my car. I'm able to stay on the call regardless of the flipping fluctuation. According to my callers, on occasion the drop from three bars to one bar and up to three again on 2g network will cause my voice to shutter.  Keep in mind that no cell company has coverage in every area that one travels through. I drive roughly 150 to 200 miles a day mostly through rural and farm areas I spend a lot of time in my car  All things considered it works well.