This is a spacer I made for my Longshot Roboman plunger rod. It's the cool one with an x-ring and carbon fiber. Put this at the front of the carbon fiber to better center your spring and prevent damage to your plunger head and tube.
I know that this adds mass, but its cleaner and less annoying than... Cartaya's tape method.
This probably also works for the spenceworkz rod, because he copied it lol.