The invention provides for a print engine for a printhead assembly. The print engine has a refillable cartridge that includes a body defining a plurality of fluid chambers, the body having a lid assembly including a plurality of ink refill ports leading to respective fluid chambers and an actuator to actuate a refill unit. The cartridge also includes a number of micro-electromechanical nozzle arrangements configured to operatively eject printing fluid onto a printing medium, and a fluid distribution member operatively arranging the nozzle arrangements in fluid communication with respective fluid chambers. A refill unit is engageable with the lid assembly to actuate the refill unit.