A liquid cartridge includes a first surface, a second surface spaced apart from the first surface, and a third surface extending between the first surface and the second surface, with a liquid outlet through the first surface. A circuit board is mounted on the third surface. A locking mechanism includes a locking surface that extends above the third surface, and a liquid detection mechanism includes a light access portion. The light access portion is disposed between the circuit board and the locking surface, and the circuit board is disposed between the first surface and the light access portion.