For what does WP generate Thumbnails?

Unless you have embedded images at the medium size into posts or pages, then WP will not use these images sizes as far as I am aware in any place in the admin.

I think it should be safe to delete the medium size images completely.

Also, I am happy you are using FooGallery – but keep the default thumbnail size, as FooGallery uses these to show thumbs when creating a gallery.

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