Check this out for me please. I've got the front for this, but it says Dura Ace only cassettes.
Pasted from CRC
WH R600 is based on the proven technology of the Dura-Ace wheels but offered at a more affordable price point.

Features:
• Ultegra wheels offer proven technology based on the Dura-Ace WH 7800 wheels
• Built with 20 Stainless steel bladed spokes at the rear, and 16 at the front
• The rear wheel uses a special wide flange hub design and an asymmetrical Rim that results in additional stiffness and stability
• Super polished ball races for high precision, durability, and smooth rotation
• Lightweight aluminium Freehub body for 10-speed cassettes only
• Clincher Rim only
• Weight: 912 g rear, 744 g front

*Please note: Freehub suitable for Dura Ace cassettes only*

Cos its a light alloy freehub, and dura ace cassettes are alooy so they wont muller it like a steel one will?

probs. Not exactly light though!

The freehub body on that wheel is a deep spline body so you are limited on what you can run. DA will be fine and 6600 Ultegra should be ok. That is all though.

UPDATE – I have double checked. 6700 and 5600 will also fit. When that wheel was first produced the only cassette that would fit was DA as it was the only 10 speed.

Good set of road race wheels though, yeah not light but they shouldn't fail. I had the front on my crosser for last season and it's true as a very true thing.

Thankyou Mister P.
Paid £30 new for the front, so £110 for brand new Ultegra level wheels ain't bad.

That is excellent value.