Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
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the waiver of any such right or provision will be effective only if in writing and signed by a duly authorized representative of fitbit . 

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. OPTIONS: ["Limitation of liability", "Content removal", "Arbitration", "None", "Unilateral termination", "Unilateral change", "Jurisdiction", "Contract by using", "Choice of law"].