Hi Henri,
The checkbox is an image. The images settings cannot be modified, but you can replace it with your own image by setting the CheckBox item's CheckedImage, UncheckedImage and IndeterminateImage properties - CheckBox item .
Our recommendation is to use an image - 96dpi, 16x16, as images are not re-sized when they are used by the CheckBox item.
I hope this helps.
Regards,
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