A clogged HP printhead may happen in several ways while utilizing a, compatible, HP bulk ink system for addressing, barcoding or printing on high speed, high volume mail equipment or on a industrial inkjet printer. Clogs occur when paper dust builds up around the machine - due to the equipment not being cleaned at intervals; when a paper towel, or a cotton cloth, is used to wipe off a printhead instead of a lint free cloth - allowing lint to clog the printhead; and when printheads are not reclipped during downtimes - allowing ink to harden in the printhead. Until recently, the operators only choice was to simply replace the clogged hp bulk ink system with a brand new system - hence, wasting all the ink in the clogged unit. Our compatible, HP c6119a, 412ml, bulk ink systems offer replacement printheads for when a clog occurs. Simply unscrew the clogged printhead and attach the replacement printhead - no more wasted ink! (Please note - our replacement printheads do not fit original HP c6119a bulk ink delivery systems and are only intended for our 412ml ink system).