My 2.4 measured up 2.4 inches across, controversially (on a Flow, if memory serves). Tall, though, so a very big volume It’s not so much that they’re massive, it’s more that we’re used to being lied to by tyre companies so accurately sized tyres seem huge.
On the other hand, 2.35 Highroller is titchy- as bigdan says, smaller than a 2.2 Rubber Queen. If you don’t have masses of clearance round a 2.35, then you probably don’t have space for a 2.4 RQ.
I found them a bit underwhelming tbh but some folks rate them. Not very good in the wet, bit unreliable in corners, but brilliant in a straight line.