How to stop Billboard GUI increasing in size as you move?

I am trying to make a custom name tag for the player in a filtering enabled game where the player's name is below their feet as opposed to their head. The script works fine the problem is the size of the text keeps changing depending on how far away from the camera you are.

http://prntscr.com/ime93z

The text underneath the blue circle keeps changing in size as you move away from the camera where as I want it to remain static, any help would be greatly appreciated.