Replacement polycarbonate sight windows come in 4.00" & 6.00". The polycarbonate windows have a glass type coating over the polycarbonate that is very thin. This makes the window resistant to chemicals, solvents, and petroleum oils. This thin glass coating may crack over time because the coating does not flex or expand with heat, the same as the polycarbonate window does.
Sight windows are very easy to change and it is recommend you have a spare incase a crack develops in the coating. Sight windows need to be measured to insure the correct thickness window is purchased.
Racer can choose proper sight window from drop down menu.