The item you inquired about is illustrated on page 31 of Campagnolo's Catalog 14. Part number 1029, "Guida Catena." On the same page. Campagnolo also illustrates the spring loaded chain tensioning arm as another listee previously described. It is Campagnolo part number 1031, "Tendicatena Ciclomotore."
Bill Curtis: inchpitch@aol.com
Costa Mesa, Ca