Festool Sander Pad Replacement

How to replace the pad on a FESTOOL ETS CT 150/3 Orbital Sander.
There are 3 replacement pads that Festool offers, a standard flex which is the one they sell the sander with. A stiff pad and a soft pad are optional.
The stiff pad being great for flat work, and the soft pad being better at contoured surfaces.

[@markjackson2276]

Thanks , I thought I was going to strip the hex but it suddenly came loose.

[@chrish227]

Can I put a 6"/150mm backer on a 5"/125mm sander?