Kartboy transmission mount bushings are made out of a strong urethane to replace the factory bushings that are soft, and become super weak over time. These are going to be installed between the lateral and the horizontal support of the transmission.
With that said the Kartboy transmission mount bushings will eliminate the flex that is caused by replacing the factory mount bushings that are super soft. You’re going to have improvements in the stability of the drivetrain, and you will feel a difference in shifting and you should have a little better improvement in throttle response.
Installed with a bunch of other bushings so I can't say much about this specific one. The combination though has massively improved the feel of the car. Hard acceleration used to lead to the feel of the transmission and driveline jumping all over the place under the car. No more of that with these.