XF 1.5 Old attachment thumbnails deleted when attachments are resized via Rebuild Attachment Thumbnails?

Joe Link

Well-known member
I'm increasing the size of all of our attachments. After changing the size in the options I'll need to run Rebuild Attachment Thumbnails. When I do that, are the old, smaller attachments files replaced by the new larger attachments in the filesystem or does it create a new set of larger attachments?