Advice on an amplifier topology

[TheBaconWizard]

So I'm learning about various amplifier types and came upon the following interesting circuit



I wouldn't mind building something similar. But I don't quite understand the relationship between the two mosfets in each cell, what is the purpose behind strapping them together in this fashion?

[Cerebus]

The clue is the voltage rails (±600V = 1200V overall) and the V_DSmax rating of the transistors (800V). As this is a class B topology it's quite possible for the entire rail voltage to appear across either the top half or the bottom half. Setting up the output transistors like this lets them share the voltage drop so that each pair might see 1200V, but each transistor will only see 600V and so stay within its V_DSmax rating.