Good cheap sights - TacFire Offset Deployable Iron Sight

As you can expect from the price, sight is made in China. While installing, the front side tightened up perfectly. As I was snugging the rear sight up, the threads pulled on the bolt before sight tightened. I switched screws between front and rear. Rear tightened up fine and has stayed that way. The front tightened up, then came loose as the gun was fired. I did buy a second set, haven't installed yet. May switch to a different brand. I contacted Optics Planet about screws, they suggested contacting manufacturer.