The extra APO slots powerups consist of the following powerups:
As their names indicate, each type grants an extra slot of a different feature, and the last one gives out the same, but for all features.
If all 30 spaces are already occupied by slots, then this powerup will hand out credits in Carmageddon II. This amount is the same as the cost of buying an APO point in the current difficulty level. In Carmageddon: TDR 2000, this powerup will have no effect.
It's also worth noting that Carmageddon II limits the slots per group. For instance, if you're still at the first group, you can only have a maximum of certain slots. When this maximum is reached, the powerup will behave as if all 30 spaces were full.
Also, in Carmageddon II, due to a glitch of some sort, if the player collects one of these powerups in a group lower than the number of slots (s)he has, the number of slots might descend. For instance, if the player has 25 slots and collects a powerup in the 2nd group, the number of slots might be reduced.