The bottom of my aluminum gate would always shake and vibrate every time we would close it. This acts as a second point of contact at the bottom of the gate to stop the shaking. 

The internal opening is 51mm wide x53.5mm deep. 

The total length of the dampener is 150mm. 

For added strength to handle the repeated stress of hitting the fence post, it has 4 walls, as well as 2mm top and bottom thickness. 

50% cubic infill.

I've also lowered the print speed to ensure a strong bond between layers.

You may have to sand down the dovetail joint a little to help with the tight fit (It is very snug to keep it from rattling when the gate closes).

The white version is a thinner test version. 

I recommend printing in PETG, but PLA will work if you want a shorter term print.

Please feel free to adjust the size for your post dimensions.