Why Didn't Someone Think of this Sooner?
Definition of a Gusset
From Merriam-Webster Dictionary (http://www.merriam-webster.com)
Date: Circa 1570.
Noun: a usually diamond-shaped or triangular insert in a seam (as of a sleeve, pocketbook, or shoe upper, or jeans* to provide expansion or reinforcement.
*(not in the Webster's definition)
Ordinary jeans are constructed with a single center seam from front to back and up the legs. These seams are usually sewn with a "fell" fold. This means you are wearing jeans that have 8 ply seams, and they all come together at the same place. The crotch seam of a typical jean is actually 16 plies thick!
Diamond Gusset jeans offer something totally different. The original gusseted construction incorporates a "delta" shaped piece of material sewn into the crotch of the jean. This allows stress to be redistributed around the crotch area, allowing greater freedom of movement, comfort and strength.
As an added benefit, the original set-turn-and-topstitch construction is stronger and less thick. The result is 3 ply leg seams, and only 9 ply thick at the crotch (not 16!).
