It involves a mask that goes over your eyes that flashes lights or emits a sound when you fall into the REM stage of sleep.

这产品有个面具，可以在你即将进入深层梦境的时候在你的眼部发出闪光，或者弄出一些声音。

youdao

And she added: "A mask can be worn continuously for up to eight to 10 hours, but must be replaced if it is taken off at any stage.

她补充说：“一只口罩持续佩戴可以达8-10个小时，但是期间一旦摘下就必须更换。”

youdao

If you're up for a stage role, a slightly heavier application is acceptable. But that doesn't mean look like a mask.

如果你是为舞台剧试镜，妆容稍微重一点，但不是要你化成一个面具。

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An impressive stage win failed to mask his disappointing form throughout the mountains, which led to him finishing 68th overall.

BBC: Cofidis, le Credit par Telephone