Wiktionary
anal beads
n. (context pluralonly English) A sex toy consisting of several small balls attached together in series which are one by one inserted into and removed from the rectum.
Wikipedia
Anal beads
Anal beads are a sex toy consisting of multiple spheres or balls attached together in series which are continuously inserted through the anus into the rectum and then removed with varying speeds depending on the effect desired (most typically at orgasm to enhance climax). Those who use anal beads enjoy the pleasurable feeling they receive as the ball passes through the narrow sphincter of the anus.