Yep, to give a slightly more thorough answer, voltage is voltage. As long as the added voltage of all the batteries you're using/have stacked in the tube are roughly the same, your diode will be fine. The other numbers you reference (mAh), designate how long the battery will last before it needs to be recharged.
A simple guide to battery designations:
Volts: aka "nominal voltage" tells you roughly how much voltage a battery will put out during most of it's cycle. Lithium ion cells will charge to 4.2, discharge quickly to 3.8-3.6 volts and plateau for quite awhile at that voltage. Then they'll drop rapidly into 3.3-2.8v at which point they should be charged.
mAh: How many hours the battery will supply somewhere between 4.2 and 3.0v if the load is one milliamp. If your load is say, 3 amps, divide mAh by 3,000 to get your (theoretical) run time.
Continuous Drain or "C Rating": How much amperage can the battery safely support if the device remains on for the full cycle of the battery. Pretty basic, and basically any 18650 will support the amperage load any single diode is likely to draw. Some batteries will describe C-Rating as an equation based on a battery's mAh rating, which I don't quite understand. Thankfully to the vaping world, most of the 18350, 18500, 18650 batteries you find these days will have a direct amperage rating listed.
Lastly, the seemingly meaningless numbers in larger li-ion cells (like 18650) actually describe their physical dimensions. The first two numbers describe diameter in millimeters, and the last three numbers describe length. An 18650 battery is 18mm wide and 65.0mm tall. A 14500 battery (basically AA size) is 14mm wide and 50.0mm tall. (I should give a disclaimer on that, as different manufacturers will add or subtract a millimeter or two, especially on the length.)
