6 - 12 M - Small brown/orange mark on front of the tee 

12 - 18 M X 3 - Small black mark on the back of the tee

18 - 24 M - Tiny dot on the bottom of the tee 

18 - 24 M - Yellow mark on the pocket

18 - 24 M x 2 - Slight discolouring in the bottom right of tee 

2 - 3 Y - Marked 

3 - 4 Y x 2 - Faint line going down the front of the tee 

3 - 4 Y x 2 - Small mark on the front of the tee