They have a nice thin/soft nylon on the inside and a thicker/slick outer nylon, both in ripstock.
The foot box in the TQ is 23" wide and 24" tall. The slit up the side runs up about 52" to the head hole. The head hole is elastic and 8" across. There is a 13" cross stitched in the middle of the TQ, I guess this is to hold it together since there is no "quilting".
The UQ has the same cross stitched in the middle of it. The ends are elastic and about 20" across, there is a tab on each end of the elastic for the shock cord. Speaking of shock cord it was just tied in a knot and came undone almost instantly (I fixed this issue with cord locks). There is also a tab on each side in the middle so you could string the UQ over you if in an open hammock (I'm in a WBBB so I took the cord off). The sides are just sown with no cord in them.
There is one cosmetic flaw but it isn't a big deal. My biggest gripe is that for me this is only summer quilt set that will not take me down to the advertised 40 deg F rating.