I have a Sig556 Classic and Sig556 SBR. Both have been great other than ejecting spent cases in to orbit. I recently purchased two gas valves, hoping that I might be able to weld up the holes and redrill them.

The one still in the bag and the one on the right are the two new ones. The one in the middle is out of my Sig556 SBR. The thing that I noticed immediately is that the holes in the two new gas valves are not the same size. The holes in the valve on the left actually appear to be larger than the holes in the original gas valve. The holes in the gas valve on the right are significantly smaller than either. Another thing that I noticed that seems odd is the gas valve on the left has the letter A on the opposite side as the UP designation. The original gas valve has an E at the same location. The valve on the right with the smaller holes does not have a letter. Any idea what the letters designate? The bag indicates that they were made in Israel. Given that it seems like it would take effort to drill the gas holes different sizes and there are letters on some of the valves, I find it hard to believe that the different size holes are simply a result of poor quality. Any ideas?