The document discusses Gracey curettes, specifically the 15/16 and 17/18 models. The 15/16 has shank bends similar to the 13/14 Gracey but with the blade offset to scale mesial tooth surfaces. The 17/18 has accentuated shank angles and a long terminal shank for improved access to distal areas of posterior teeth. Both provide improved access and positioning for scaling difficult to reach posterior teeth.