Set of 4 Permanent Chips for HP 940, 940XL (OfficeJet Pro 8000, 8000A, 8500, 8500A) This set of permanent chips can be used on any cartridge type, although it is mainly designed for use with either a CISS system or refillable cartridges. These chips, when installed, do not show an accurate ink level. This is not a bad thing because it means the printer will never display ink low messages. If you have a CISS or a refillable cartridge set, it is always easy to see how much ink you have left. Permanent chips give the user the flexibility to decide when to refill without harassment from the printer. The chips come with an adhesive backing and so are easy to install. These chips never need to be replaced.