The rail replaces the original rear site leaf. Once it is in the rear site block it attaches to tang with the original wood screw that is in the stock. There is also a "set screw" at the rear site block to hold the rail tight in the grooves to prevent "bounce" at the rear site leaf each time the weapon is fired.
There are not bushings in this rail and the only set screw is the one described above.
It will fit MOST AK models with a standard fixed stock rear tang. I say most because we have ran into one or two that it would not fit. It made no sence why it wouldnt fit because it was a standard Romy kit build. We have been selling these for 6 years and have only had 3 returned because they wouldnt fit.
I hope this helped.