Although in the text it's just described as "a Chinese box" with a 5000MaH battery and the ability to record to its 32Gb of space in chunks of 30 minutes, as MP3 taking about 28mb each.
That section goes on to describe trying different microphone positions, as it makes a great difference to quality. OP originally tried it in a bag but the results were medicore, so moved to a different configuration which, although less comfortable, produced superior audio results.
https://roberdam.com/wisper.html
Although in the text it's just described as "a Chinese box" with a 5000MaH battery and the ability to record to its 32Gb of space in chunks of 30 minutes, as MP3 taking about 28mb each.
That section goes on to describe trying different microphone positions, as it makes a great difference to quality. OP originally tried it in a bag but the results were medicore, so moved to a different configuration which, although less comfortable, produced superior audio results.