Piano Catch Upright Piano Insulator

I purchased this for piano installation, but the delivery personnel said it couldn't be used because the piano casters were too small, so I'm selling it.
I took out two to test and fit them to the piano casters.
It has felt on the back, so it's said to be movable.
Below is the product description.

These are standard soundproofing and vibration-damping insulators for upright pianos. They are much larger and thicker than the plastic insulators that come with pianos, strongly absorbing sound (vibrations) from the casters and preventing sound leakage to the floor below. They are essential for apartments as simple soundproofing equipment. They also have a positive effect on the piano's sound by suppressing unnecessary resonance.

●Because the back is carpeted, if you place it in a room with flooring, you can slide the piano with the strength of one adult, making it very easy to clean behind the piano.
*This product is not a disaster preparedness item.