You need to check the correct size.

How do I measure the "normal" trailer?

awning size

First place your caravan on a flat surface. Start at point A and measure through the caravan rail to the ground on the other side point B.

How do I measure the aero / oblique caravan?

awning size

If you have an aerodynamic trailer, you should at the oblique at a height of 185 cm right to the ground to measure and not the caravan rail further.