Cheek pads in all sizes helmets interchangeable. So in an XL helmet you can place M cheek pads, if you think they should be a bit thicker than 15 mm. Please note, 1 cm thicker cheek pads go 2 x 1 cm = 2 cm thicker in total.
Cheek pads of the BoXXer and the BoXXer Carbon are interchangeable. The Carbon variant has a velvety texture against the skin.