I think they're good value if you're not looking for something 'authentic',
I have a UTG Pro quad rail on one of my ARs and til recently had a UTG Pro quad rail on my WASR but removed it and went back to my Leapers side mount. The Leapers side mount top rail sits a little higher than the UTG side mount, just enough to remove the receiver cover without having to remove the mount. The UTG looks better and is probably much lighter.
And for anyone who cares, the Leapers side mount is at the same level as the top rail of the UTG Pro quad rail. I know because I had a reflex sight on the quad rail and a compact scope w/low profile rings on the Leapers, each one was previously sighted in @ 100 yards and one day I was swapping between the two and happened to sight down the barrel with both on and the red dot appeared in the center of my crosshairs at lowest power (2x).
Afer swapping my plywood stock for a fixed poly stock the quad rail & reflex made my stamped AK way too nose heavy, going back to the wood handguards felt like taking 5 pounds off the rifle. I'm back to iron sights and occasionally use the scope & side mount for long distance shooting.