Some chains, including Shimano®, use chain rivets which are peened. This creates a "mushroom" effect at the ends of the rivets, which adds to the strength of the chain side plates. When a rivet is pressed even partially out, this peening is sheered off on the side pressed by the chain tool. If this rivet were reused, it would create a weak link at that rivet. In the image below, a Shimano® rivet is shown in an optical comparator, which magnifies the rivet. The original peening is seen at the bottom of the rivet. The top of rivet has the peening sheered off. This top section was pushed through the outer chain plate.

Shimano® chains use a special connecting rivet when the chain is installed new or when one is removed and re-installed. This connecting rivet has special flaring that is guided in by a long tapered pilot. The pilot is then broken off before riding. Only Shimano® brand chains should use the Shimano® connecting rivet.

The 7 and 8 speed chains use a black connecting rivet. The narrower 9-speed chain uses a silver-colored connecting rivet. The Shimano ® CN-7800 chain for 10-speeds uses a silver colored rivet with an extra-machined line for identification on the pilot. The Shimano ® CN-7801 chain for 10-speed sprockets uses a connecting rivet with three machined identification lines. The 10-speed chain rivets are not interchangeable.