It's definately whole units, no halves as with the NovoPen 3.
However, it's really light to us, and you can simply wind up or down units, no need to pull the 'barrel' out to reduce... positive dialing of units and just works well.
My two critiscisms (besides half units) are the case, I much preferred the solid case of the 3 and the fact that STILL they don't supply optional barrels for insulin types - sure there is blue and silver, an orange barrel for NovoRapid and a green on for Levemir and a Yellow one for the yellow case insulin (ok, brain fuddled!).
The best they offered me when I raised it years ago were a sheet of paper stickers - YUK.
Having injected 20 units of NovoRapid thinking it was Levemir once, I don't ever plan on doing that again! So I ended up painting the end where your thumb is in the kids War Hammer paint - it works!