MB Technology’s SBS Shingle Starter is a premium SBS modified starter strip completely coated on both sides with SBS rubberized asphalt compound and surfaced with black ceramic granules. The SBS rubberized membrane provides a flexible starter roll and, because it’s non-porous, it provides a watertight membrane by itself. The fiberglass-reinforced product is used for eave and rake starter material for composition roofing. It is used with minimum 3/8-inch head roofing nails, fastened 12 inches on center and at 4 to 6 inches above the edge of the roof or as required by the shingle manufacturer.
Source: roofingmagazine.com =>Shingle Starter Material Is Non-porous