The Equal Air deflator will deflate or inflate two tires at the same time.   It comes in a hard plastic storage case with the deflator and a low pressure gauge.

 

Inside the box you get the Equal Air, a low pressure gauge and instructions.

When I first opened the box, my thought was "this will never go back into this tiny box after I use it."   After I used the Equal Air, I was actually able to get it back into the box without any problems!

Here is a close up of the pressure gauge and release valve (green arrow).   Once hooked up to the tires, the gauge will show the current pressure.   To release air, slide the valve down to open it (shown open, you can see one of the air passages).   When you think you are close to the desired pressure, close the valve and check the gauge.

There is also a standard schrader valve on the end (shown capped) to add air.   You can also use the included low pressure gauge here for greater accuracy.

Here it is hooked up and ready to go.   The central valve lets you monitor both tires at one time for both airing up and down.

This is a great item for those people that are super picky about their tire pressure (I know one!)   Instead of having to check and adjust the tires one by one when airing up and down, two can be perfectly set at a time!