Real Sword PSO, originally sold with the RS SVD.
I am the XY owner; it has some history and dates back to when the RS SVD was first released. Since it was designed specifically for airsoft, it offers a much wider range of reticle adjustment compared to the real-steel PSO. This makes it significantly easier to zero on airsoft replicas, including those where other PSO copies fail to work. It features a clear image and is arguably the best PSO for airsoft.