A flat ring pressed around the hole in a 5.25" floppy disk for rigidity. The drive's clamping ring presses the hub ring onto the spindle.
"hub ring." YourDictionary, n.d. Web. 24 May 2018. <http://www.yourdictionary.com/hub-ring>.
hub ring. (n.d.). Retrieved May 24th, 2018, from http://www.yourdictionary.com/hub-ring