Review on Energy Suspension - 2 Pack of 9.9101R All Purpose Bump Stops - Optimize Your Search! by Sam Davenport

It worked perfectly for the purpose it was bought for. The material is much harder than what is typically used for this type of application. So when you push down on the bumpers, it's comparatively a lot stiffer. However, you can "tune" the impact force by enlarging the center hole and/or adding a soft rubber washer between this element and its mount.