Simple blur in unity 2019?

Hi, I am making a FPS game and I wish to blur part of the screen when aiming a weapon. This blur should be adjustable in intensity. In unity 5, there was just the standard optimized blur script. I found that script somewhere in my old projects and it works in editor mode, but not on runtime. Is there a simple way to fix it or are there other methods to create blur in unity 2019? All the methods I could find so far are either not longer working or just plain sketchy. Kind regards, Rens