As others have said, they do not fit the 507. The slot in the replacement brush is too narrow, much smaller than the standard brushes that come with the 507. You can force them on (I once did), but I didn't want to damage the brush and get "duct tape" (another reviewer) or a new 507 (it's an excellent electric brush). Came back for the 507. Those who say they are "perfect" for the 507 either got a different product than I did or they just put them in their place without much thought.
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