The puma boxer briefs are pretty crappy. I have purchased many different brands of boxer briefs in my time, such as Puma, Calvin Klein, Gold Toe, Lucky Brand, Polo, J.Crew, and on and on. The Pumas are the worst. They are better than fruit of the loom, but really, that's not much of a compliment.
They stretch out immediately after you put them on, are really thin, and the elastic doesn't last. Maybe they are worth $4 a pair, but then the shipping... I'd stay away. Shop the Marshalls and TJ Maxx clearance sections for good underwear deals. Lucky Brand is nice and they regularly make it to clearance.