Okay, I fixed up the 'slot car' bit. Changed it to 'die-cast car'. Even though most people have already visited this topic already.
I didn't realise until now that 'slot car' was not the appropriate term, as it refers to those electric race-track sets, which these RPMs are not.
I couldn't use 'Hot Wheels' type cars, because that's a brand name, and a competitor at that.
Calling them 'die-cast' cars doesn't specify how big they are, so I guess it is just automatically assumed to be that standard 'Hot Wheels' size.