At Initiative Step 10, a charging model part with Impact Hits must choose an enemy unit that is in base contact with the attacking model's Front Facing. This unit suffers a number of hits equal to the value stated in brackets (X). These hits are resolved with the attacking model part's Strength and Armour Penetration.
If a model has both Grind Attacks and Impact Hits, it may only use one of these rules in the same Round of Combat (its controlling player may choose which). In multipart models, only model parts that also have Harnessed or Inanimate can use their Impact Hits. When several models in the same unit have Impact Hits, and when X is a random number (e.g. Impact Hits (D6)), roll for the number of hits separately for each model part.