II dont think its an exactly 18 percent gray card. According to my tests with two different cameras photo and video, the image gets a little too bright respectively, the gray card itself is a little too dark. Once accustomed, one can keep in mind that it needs to be done darker than the gray card indicates. The white balance gets correct. The rim could be more flexible to fold. Translated via google translator
Fast delivery. Quality goods, as described. Thank you.