The Monitors were originally designed just for the piano player which is why they ship with brackets as they can be directly mounted on the following specific models:
Nord Grand, Piano 4, Piano 5 73, Piano 5 88, Stage 3 (revision B 88 & HP 76 only)
These instruments in the Nord range have additional screw holes on the back which the brackets attach to, allowing you to have the Monitors mounted in the optimal listening position, without the need for speaker stands.
Of course, the Monitors will work with any of the Nord keyboards – just put them on normal speaker stands or a shelf and connect them up to your instrument’s outputs using the supplied ¼” jack cables.
Dimensions: H220 x W150 x D198 mm
More info can be found here.