If I run 1×9 what chain device is good but in a xc rather than burly DH way, has to fit frame without chain device mounts

MRP 1.X and E.13 XCX are the common ones.

N-stop chaindevice..

SkoolShoes had built a rather smart one for £15 that weighed nowt. Thread about it last week. I've a Paul's Comp one, pricey but nice. I've not really tested it yet.

n-stop and bash on a budget.

rohloff if you're feeling rich.

but it is possible to run a tight chain with a shorter-cage rear mech, and unramped chainring w/o a chain device. not tried it but apparently its do-able.

I got an MRP its 58g it doesn't look much but the mount is all cnc and nice when you get it and its dead easy to set up too. It does have alu bolts though and they are not joking about using a new and sharp allen key to tighten them, its all good thou you dont need to do it if you split your chain and thread it through. I love it, if you have a decent rear mech you can forget dropped chains and you stop fantasizing about internal gear hubs too.

Pauls Components Chain Keeper here, works great, no problems.

MRP one worked fine for me. There was one advertised up there ^ recently which had a plate on each side of the ring to keep the chain on, looked good.

Locked off derailleur? I've had less chain drops running dual with a normal derailleur than I did with 1×9 and full dmr chain guide.

n stop and ti bash ring off the guy on here that sells them, v light, and £20 for the ring £10 for the nstop

nice TimDrayton, very simple, i like it

Another vote for Paul Components Chainkeeper; very minimalist – but very effective. And better than the MRP 1.x I had before it; the 1.x was a hoover for mud and woodland detritus.

That is a really nice setup. Me wantee.

"There was one advertised up there ^ recently which had a plate on each side of the ring to keep the chain on, looked good"
They were really really pricey and they bolt onto the inner chainring mounts (so chainline can't be good?), they seemed to think that a 32T front ring was to hard to try out* 1×9 so a 28T or 30T is where you should spend your money, you'd be dropping loads of gears of the top end, but barely any at the bottom, which seems to defeat much of the point of 1×9
*if you are trying it out you wouldn't be shelling out £50+ or whatever it was

"n-stop and bash on a budget"
CRC have FSA bashguards (inc. long chainring bolts**) for £16 (or they did)
**the £20 truvativ one on CRC doesn't have any