These should be drop-in 3D printed replacements for the original metal guides that can become worn/bashed, causing excessive ball hop.
The design also features an extended tip which closes the gap to the flipper. This further decreases the potential for ball hop, even for a slow rolling ball.
There are two versions, one has holes, which can allow more light through. The other one more closely mimics the original design.
You may optionally try some of the posts, which are slightly shorter and may fit better as this model is 1mm thicker than the original metal guide.
The author marked this model as their own original creation.