One Internet firm boasts 900 different types, made from dozens of different materials, for use either indoors or outdoors.

一个互联网公司拥有900个不同类型，使用来自几十个不同的材料作出，无论是室内还是室外。

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We arrived at the hotel, unpacked and quickly dressed for an event that could either be indoors or outdoors.

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No special equipment is needed (although a heart rate monitor can be helpful for gauging how hard you are working) and interval training can be done either outdoors or indoors.

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