Labeling yourself to be "the world's best" anything is ballsy. Which is why I reserve a modicum of respect for anyone who boldly makes that claim. And while I'm not a fan of hyperbole for products as simple as a shirt, there might be some actual merit to Mr. Davis' claim.
What makes these undershirts the best in the world? According to the product page, they offer "comfort like you've never felt from a shirt," a fit that's "snug without being tight," and the ability to be practically invisible when you wear it under your favorite custom dress shirts.
Mr. Davis undershirts are made out of ultra-thin bamboo fabric (96% bamboo, 4% spandex) that stretches omni-directionally, ensuring they won't constrict your movement. The material is supposed to be so comfortable, "you'll never be happy in cotton (shirts) again." Not only does it boast great fit, they're also cut to be longer in the back than the front to ensure they remain tucked in even when you move around. While most of us have long accepted that undershirts will be visible when wearing shirts with thin fabrics, not this one; instead of being white, it comes in a hue they call "tone," which "virtually disappears," so it looks like you're not wearing any undershirt.
For now, they're only offering a v-neck version, so those who prefer flat collars will need to compromise if you want "the world's best undershirt" in your closet. Currently, Mr. Davis is collecting backers on Kickstarter. Pledges to reserve a shirt start at $20 (yep, the world's best undershirt is only $20).