Many quarter glasses come to a sharp point in the back and can be difficult to remove. These blades are designed to reach into those difficult areas and cut the urethane. They are also very useful on those vehicles that have corners with sharp angles. It can be very challenging to reach into some of those corners to cut the urethane. The blades are very flexible to allow the tool to be held outside the quarter glass opening while cutting inside the opening. Each blade is designed for a specific side of the vehicle.