I’ve just ordered loads of stuff for my new build, including a 42t sprocket and foolishly in all my excitement about new bits an slx 11-34t cassette, despite the oneup site specifying 11-36.
Do I need to order a 36t or could it work?
34 to 42 is a bit of a jump..
Can’t change the order as i bought a chain and cassette combo on offer at merlins..

Don’t you need an XT cassette anyway?

You can use an slx cassette, just needs a bit more work

a) Give it a try…can’t do any harm. If it works, great, if not sell it on and put the money towards an 11-36 SLX ot XT.

or

b) Order an 11-36 SLX, and send it back saying it was an 11-34 in the box.

I would do a) cos it’s the right thing to do.