?Durable The bubble shell is made of good quality plastic. ?Universal Made for golfers, amateurs, and professionals. ?Accessibility The built-in bubble level on the marker shows you the slope & incline on the green to help with your read. ?Convenient Using magnet, easy to stick on and off, attachable on hat, belt shoes with the clip equipped. ?Professional Designed for golfers of all types. The bubble level will train your eye to see the subtle contours that can make even a short putt difficult. More use, the better your putting game will be.