This is a bag of 3 Shimano 10-Speed replacement chain pins. Simply discard the original pin when making a repair and replace it with this special replacement pin. The extra long size includes a narrower starter section for easy entry to the link. This allows for a much easier reinstall of the pin, no more fidgeting, and cursing at your chain tool. Once the pin is pushed through the link, simply use a pair of pliers to snap off the extra bit at the pre-set perforation. Good as new!