Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
any delivery dates or times provided by us ( or a courier ) are estimates only and are not guaranteed . 

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