That is , a reasonable part.

不大不小的一部分.

英汉文学 - 三万元遗产

When I placed the medal in his hand, it fit perfectly.

我把金牌放在他手里,不大不小, 正合适.

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This machine base is exactly the size of my cellphone.

这个机座不大不小,刚好放下我的手机.

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He have an average - size office.

他拥有一间不大不小的办公室.

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There is a spider mole that is neither too big , or small on his face.

他的脸上有颗不大不小的蜘蛛痣.

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