And they suck. I've got a buddy who has the one with the set screws on the side, and in a ddition to not clearancing properly on the bolt, it STILL can't hold it's zero. I'd see if you could get an original topcover, if you don't have it.
Only 2 ways I've seen to mount optics decently on an SKS; red-dot/scout scope on the gas piston block where the rear sight was, and modify the stock to mount a tall rise scope rail to the side of the lower....