-Retractable,pen style barrel -Fish hook groove -Flat side for straight ... Diamond Hook Sharpener(Buck Diamond Pocket Knife Sharpener)-Retractable, pen style barrel.-Tapered end for serrated blades.-Fish hook groove ... durable enough for field use.-Optional Grit: #300(Medium), #400(Fine), #600(Extra Fine)Optional spec.: (1)Diameter 6. ... (2)Diameter 4mm x Length 70mm Electroplated Diamond Sharpening Pen