In one example in accordance with the present disclosure, a fluid ejection system is described. The fluid ejection system includes a frame to retain a number of fluid ejection devices. Each fluid ejection device includes a reservoir disposed on a first side of the frame and a fluid ejection die disposed on an opposite side of the frame. Each fluid ejection die includes 1) a fluid feed slot formed in a substrate to receive fluid from the reservoir, 2) an array of nozzles formed in the substrate to eject fluid, and 3) an ejection adjustment system to selectively adjust an amount of fluid ejected from the fluid ejection devices.