Laser Tek Services 4 Pack Toner Plugs made specifically for Canon and HP Printers Toner Cartridges that have a plug in them. These plugs are used to replace the old toner plug after refilling the cartridge and come in handy if the old toner plug is damaged in the refill process.
Here are some of the cartridges and printers that these plugs work in (Note: These plugs can NOT be used in cartridges that require burning or cutting a hole in the cartridges):
Canon X25, Canon S35, Canon FX-3, Canon FX3
HP C4092A, C3906A, 92A, 06A, C7115X, C7115A, 15X, 15A