I just got one of these today (The Mini 5100c) and this is one of the greatest pieces of hardware *ever*. Less than half the footprint of the gosh-awful MS ergonomic that came with this computer, and all of the keys are in rational places.
Keyboard dimension: 297(L) x 151(W) x 39(H) mm
Keyboard weight: 0.65 kg
BTC Products - Mini Keyboard