I'm sorry but this is the first product on OOD that I can't recommend, firstly they don't fit on standard 130 motor shafts so there isn't even a point in getting them(and it wasn't that I wasn't pushing hard enough, I used enough force to accidentally bend the shaft of one of the Kraken motor's I was using)(it also broke though 2 of my 3-D printed flywheel cages while trying to get them on). Soon further inspection on other sites I found that these not fitting on 130 motors were a common occurrence :(. Also when I flipped them upside down and spun them they seemed to be slightly misbalensed. I'm very disappointed in these flywheels, I had very high hopes for them :(