That is an anti draw through version. The tubes have nothing to do with the actual size of the stream. Think of it like a hooded Holley nozzle.
It's kinda like a doctor or a dentist.Everybody knows about them. Nobody knows what they do. But if you need one there's no bad ones.
Right? I don't care how bad a doctor or a dentist is; when my kidneystone is moving, or I have a tooth that needs attention right now, I am glad to see him. Very glad!