Korg micro-Arranger: .75" Wide x 3.1875" Long

Yamaha Tyros 4: .875" Wide x 5.5" Long

Steinway B Grand: .875" Wide x 5.875 Long

The actual key height of each of the above keyboards is difficult to accurately measure
because Tyros 4 doesn't include a straight down vertical front like the Steinway and Korg microArranger have.
Also,, the lowest portion of the Steinway and micro Arranger's key fronts (vertical measurement)
are partially obsured behind the fall board.

Reviewing the measurements,
the main key size difference between Tyros 4 and the micro-Arranger
is their respective key 'length'. Tyros 4: 5.5" ; microArranger: 3.1875".
On the other hand, the microArranger's key 'width' is only .125" narrower than Tyros 4.

Scott