The weather resistant stripes are stripes around the top of your quilt and foot box that are 20D fabric instead of the normal 10D which gives you more moisture control and durability around the problematic areas of the quilt while still giving you the breathability of 10D in the middle of your quilt. The top stripe is for breath condensing under 30° and the bottom stripe is for when rubbing against the side of your shelter. If you chose a 20D material for the outside of your quilt already, you do not need the stripes as it would be the same material.
We offer the stripes on almost all our quilt style sleep systems, but there are a few that we cannot add them to. Our sleeping bags cannot have stripes added to them, and this is because of how they are produced. While most of our products use templates that are horizontal when we cut the fabric, the Convert and Conundrum's templates are vertical. This makes it so we cannot add the stripes to these particular quilts.