Is this a approved underlayment for a comp shingles? If so, who is the manufacturer?
The material (seen at an eave) in not adhered to the sheathing and very flexible - it feels (and looks on the underside) similar to ordinary black 4mil plastic sheet.
At other locations there was no underlayment at all, there were no drip edges at any location I checked, and the roof was a low-bidder job in other ways (including retaining existing shingles in areas where it would have been little additional effort to replace them).
So it would not surprise me to discover that this material not intended for use as underlayment at all, however the textured upper surface and white stripe suggest it was manufactured for some specific propose.