I’m in the process of building my first geared mtb having ridden single speed previously.

The build is middleburn uno with SRAM xo 1×10 med cage.

Will I need a guide?

Cheers folks

maybe.

Probably.

*re-reads OP and upgrades recommendation to ‘yes’*

Unless you’ve got a narrow/wide chainring you’ll need a guide or the chain’ll bounce off fairly regularly, even with a clutch mech.

narrow wide + clutch mech might be OK,
i needed one for mine when riding rough stuff got an MRP 1x upper guide and its groovy

Ride it. Does you chain fall off or not? You will then be able to satisfactorily answer your question rather than stirring up disagreement on here 🙂

i have middleburn uno and Shimano Zee short cage

i have ridden Cwm Carn and innerleithan on both the DH and XC tracks and the chain only came off once on Cwn Carn XC

so presently no plans for chain guide – as soon as it starts to fall off then i’ll get one, so with stilltortoise on this one

i prefer the look without guide though

Ride it. Does you chain fall off or not? You will then be able to satisfactorily answer your question

This is the truth.

As a matter of opinion however, yes if you are a serious racer and no otherwise however if you asked whether you should get a skinny/fat and a clutch-mech then the answer is yes.

I run one bike with a N/W and non clutch X9 rear mech & another with std csingle ring & Deore clutch mech. Not dropped the chain on either in a good 3 months of use without a chain guide but before I ran either the N/W or clutch I had to use a chain guide as I dropped the chain regularly, especially on fast bumpy sections.
Based on my experience, a minimum of the ring or clutch mech or chain guide, probably be better with at least 2 of them for security.