Hanes 738994509994 Mens Ultimate Comfort Fit Crewneck Undershirt, White - Large - Pack of 5

These shirts are comfortable and long enough to stay tucked in if you get the right size. However, choosing the right size can be challenging as I have found that the color of the shirt somehow affects the size. For me, 5'8", medium in white, large in black, and probably medium in gray (I purchased large). The gray shirts in this pack are wider and longer than the black ones after washing and I have found white shirts from a previous purchase to be similar.

The only drawback to this shirt (and why I give it 4 instead of 5 stars) is that it's about 2 inches too long. They used to be shorter, so it was a nice, trim length; now it's a bit like a dress, so that's not great. It's a great shirt, they just need to crop it a bit.