The default behavior of an accordion pane (C1AccordionItem) is to fill only to the height (for accordions that expand up or down) or width (for accordions that expand right or left) of an accordion pane's contents. This will cause the accordion to grow to different heights or widths depending on the height or width of the content for a given pane. This is illustrated in the example below.

To avoid this, set the height or width of the C1Accordion control and then set its C1Accordion.Fill property to True. This will cause each panel to expand to fill the width or height that you specified, thus providing a uniformed width or height for accordion pane. You can observe the difference in the example below.