Wow. You can't beat the price ($1.38). It costs more for a cup of coffee at the local coffee shop.
Yeah , I think that it will work with a 20x4 display since the parallel connections for both types of
displays are the same. You have a display with "n" connections and a black box with "m" connections
and the software sends what it needs for the type of display you want to control.
If you don't have the configuration info you can find out using a program called a "GUESSER"
that tries different configurations until it gets a match and then prints the configuration to
the serial port where you can see it using the serial monitor. You have to change the serial monitor
Line Ending to "Newline" for it to work. Read the instructions in the code and when you get the
config info paste it into an lcd example sketch from the library. http://forum.arduino.cc//index.php?topic=157817.msg1235230#msg1235230
You'll need the library from here to use the guesser. https://bitbucket.org/fmalpartida/new-liquidcrystal/downloads
If you don't know how to change libraries then ASK.
when you try the guesser , if you have a 4-bit parallel display available PLUG IT INTO THE ADAPTOR because when
the GUESSER finds a match it will BLINK THE BACKLIGHT 3 TIMES and then DISPLAY the CONFIGURATION
(ie: "lcd(0x27, 2, 1, 0, 4 ,5, 6, 7 , 3, POSITIVE)