it is called the "V-plex wide". A wide portion of the reticle is pretty thin like a normal FCH reticle, and then it steps up to a little thicker line around the edges.
I have looked thru Vipers in every reticle they offer and this is actually the one that I prefer the most. It is perfect for both target and varminting, as well as game hunting.
If interested, I also have Viper with a Target Dot on another rifle that I would sell instead. It is in the same condition as this one.