New 11-42 XT cassette
New Hope Pro4 12×148 hub
Spacers that came with cassette (2 of) in correct sequence throughout to spread of the cassette.
Lock ring tightened down to 40 nm with torque wrench.

Cassette is very loose on freehub to the point of rattling/ rocking.

What have I missed here ??

Pro4 is an 11 speed freehub, so needs a spacer behind the cassette to run your… 11 speed cassette. Go figure. One should have been in the hub box, or supplied with the wheels if hope hoops.

Pro4s use an 11spd road freehub body. 11spd shimano mtb cassettes are designed to run on 10spd freehub bodies so you’ll need a spacer as benpinnick said.

Aha picked the wheels up today which have been built for me and no spacer given or present.
Pro 4 to DT 481 rims.
Many thanks thought I was going mad !

Is the spacer behind the freehub the same size as the other two ?

No its 1.5 mm thick I think (as opposed to 2). Call the builder.

Thanks will do.

I just checked and its only 0.3mm between the hope spacer and a 10spd cassette cog spacer, so I am willing to take a punt and say you’d be ok with harvesting a spacer from an old cassette and using that. An 11 speed one probably even closer to the right size (contrary to my earlier comment on that).

Think I have some left over from a 10spd cassette.

Just put the 10sp one on and cassette is now steady on the freehub.

Glad I read this last night.
Just found the same thing on a new pro4 boost wheel with 11 speed XT cassette.
Put a BB spacer in for now until I can get the correct spacer.
Am I correct in thinking the spacer should be 1.85mm?

Hope measures 2mm (1.98mm on my Mitutoyo callipers)

Cheers gravity.