To minimise the amount of material in the piece, the cassette itself is machined from a steel forging to make a hollow cone (called PowerDome) with a series of concentric steps on the inside, each of which coincides with the base of one sprocket. Eight individual sprockets are machined on the outside. The inside face of the largest sprocket, which forms the base of the cone, has an inset shoulder with tooth forms, which match the shape of the aluminium plate that forms the inside face of the cassette. A sleeve fits between the face plate and PowerDome to support the plate when the lockring is tightened.
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