Silnylon comes in 1st and 2nd quality.  Certain colors used for tarp doors made from Silnylon 2nds.  Using Silnylon 2nds keeps the cost down and 2nds have only slight cosmetic imperfections (or none at all) and does not diminish the integrity of the material.

Sewn on doors and center pole pockets

Need more room under your tarp?

The center pole pocket mod opens it up right where you need it most.

Adding doors provide storm coverage and gear storage areas