The domes are 50mm in diameter and provide a uniform surface to apply pressure too no matter what the foot angle is.
They rubber up over time to give a consistent hard foot.
For boards <40Áš they are quite kind.
>40Áš they turn into a hellish battle of core vs foot traction.
If you do circuits they are a fantastic addition to lesser angled boards ~20Áš in angle and give a really good pump in the core that soon works its way up to the fingers.