Racer can find their fuels specific gravity and percentage once they choose a nitro hydrometer from 0 to 50%, 50 to 100% or gas/alcohol hydrometer bulb from drop down menu. Enderle hydrometer bulbs have the temperature thermostat built into them for an easy to read application.
Some of the legendary nitro tuners like to carry two hydrometer bulbs to compare and make sure everything is right where they want it with no variables left on the table.