On a TIE Pilot helmet, the back of the helmet arches up enough that your neck and lower portion of your hair is visible from the back. This really ruins the illusion of being in a sealed flightsuit… just like having the back of your neck exposed in a Vader helmet. You must have some covering for your head when going TIE.
There are three ways of handling this. You can either… A) cover your head in a balaclava; B) at least cover your neck with a neckseal; or C) use both a balaclava and a neck seal.

I personally use both. I feel that it gives you complete coverage, and the neckseal gives you a unifying look with your fellow TK’s [Stormtroopers]. It just looks better, in my opinion.

The balaclava I use is made from a lightweight cotton. It breathes well, and I’ve found that it is excellent for wicking up sweat while you are wearing your helmet. The one I went with was purchased from Sportsman’s Guide. Here’s a link. It is inexpensive [$7.00], so I bought a spare. They are washable, which is important.
For the neckseal, I found one that looked great on eBay. After the fact, I found their website. There are several sources for neckseals. Do your research and you’ll find them easy enough. I am very pleased with the one I purchased. It is made from washable cotton/lycra. It has 7 ribs, the same as a “Hero” version of the Stormtrooper neckseal. The neckseal goes on like a dickie, with the front and back cloth portions tucked into your flightsuit. The back of the neckseal is split, with Velcro at the seam.

Tutorial used courtesy of