The exact tool we recommend for tightening or loosening the seat-post / saddle-clamp nut on every Rock the Bike frame with a square seatpost. Slip the 13 mm closed-end over the nut, clear the frame with the 40 ° offset, and apply smooth, confident torque from the 9½-inch handle.
Keep one in your event kit for emergency tweaks. There’s no better fit.