Ok I've done my reasearch was going to get viper pst ffp ,now I don't know. I wanted wind drift on my tourrett . Kenton does not do pst .vortex said gunwerks would ,I called them only if you buy there shooting system. The man at gunwerks was a nice guy he said just get a paint pen and put drift on myself I guess I can do that. If I buy mark 4 ,i don't have to put it on myself kenton can plus its a mark 4 ,what do you guys think.