This doesn't work miracles but it works well.  I use it all the time for car camping and it's great.  iPhone 6 fits.  It typically boost me about 2 bars, including from none to 2 (if there's any signal at all).  (Using tech app, it'll do something like -107 db to -85).  It gets quite hot, don't put it in the sun, but the heat has never melted or harmed anything.