Rear chain guide

I've seen posts proclaim TMD's chain slider for a modern KX250 works on our bikes, but I'm a cheap-ass, so I figured I'd try Primary Drive's guide since I use one on my YZ250F and like it.  It's close, but not perfect.  You have to modify it some and it doesn't line up perfectly, but it worked fine in a 110 mile dual sport yesterday.  I selected 1999 KX250 at Rocky Mountain to order it.  You basically have to plane down the upper middle plastic piece slightly and then ream out the 3 mounting holes one size larger to get it to mount.  Pics:

I don't want to sound like a dick but the stock one is much better than that one.

The good rear chain guides have plastic in them that's only a hair wider than the chain guiding the chain straight onto the sprocket, the primary drive one doesn't have it leaving room for the chain to move sideways, the chain can get shoved off the sprocket easier than stock.
Were you suppose to put the plastic out the stock guide into that one before installing it?

I put a similar guide on my yz(its a fredete racing one, looks identical other than the color, it was free to me it came with another bike I had) I cut a piece of 1/4 inch thick uhmw plastic (an old cutting board) to fit inside the guide taking up the space between the guide and chain, I could only get it to fit on one side, its on the out side of mine, theres only a 1/8 of an inch from the chain to the guide on both sides of the chain now, its better than it was but still not as good as the oem one on the wrr, the tmd ones are a setup from oem too.

I really don't give a damn about your opinion of PD's chain guide design.  It definitely withstands a beating and bends back into shape way better than the stock guide.  It does not have plastic on the sides, but it has it where it should, above and below the chain.  You could argue that it should have it on the sides, but my experience has been that the only time the side plastics gets rubbed is with a bent guide.

I guess I wasn't clear.
With room between the sides of the guide and chain a stick or rock can get between them and push the chain off the sprocket, that wont happen with a stock guide.

There's a reason everyone pays a little extra for the TMD guide, its the best one going.