They aren't silent as such, but they make a hell of a less racket than normal ones. I've had to buy a new one though, because it got very noisy through wear.

Due to the actual running on the wheel and friction, it would be impossible to have a completely silent wheel.
Also, some noise comes from what the wheel is on, rather than the wheel itself. For example, I find that when fixed on the cage bars, it causes the bars to resonate, but when it is on the stand in the tank, it wobbles a bit more on the floor.

But still, much much quieter than say the savic ones.

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