BioThane Fan Holders are available in several sizes.  The 7" fits the Small & Mid Size Ruffland Kennels. The 9" fits the Medium & Intermediate Ruffland Kennels. The 10" fits the Large & Extra Large Ruffland Kennels. Proper sizing is important to allow the outside rings to fit properly and keep the center ring in position so the fan is centered on the lower portion of the door.