撇开美学的差别，唯一的物理差别就是在较便宜的HD 555耳机内部多了一块泡沫，阻挡了约50%的外向通风孔。

Aside from the aesthetic differences, the only physical difference was an additional piece of foam inside the cheaper HD555 headphones, blocking about 50% of the outside-facing vents.

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柴油还含有优质的清洁剂便于发动机内部的清理，这就转化成了发动机的低油耗以及良好的行车里程优势。

Diesel oils also have superior detergents to keep the engine's innards clean. That translates into lower oil consumption as well as better mileage.

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小一点如米粒大小的传感器可以被航空公司用于在飞机内部检查是否存在可能干扰线路的大昆虫或啮齿动物。

Smaller versions the size of grains of rice can be used by airlines in the innards of aircraft to check for the presence of large insects or rodents that might interfere with the wiring.

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