This is Japanese paper that prevents ink from bleeding through. It can also be used when using a stamp. This is the text from the sales site of SAKAE Technical Paper Co., Ltd. ↓↓↓↓ A5 Semi-size Blotting Paper (Bamboo Neutral Paper) BWA BWA-SA5 A5 Semi-size 143mm x 205mm 10 sheets Blotting paper, used as a companion to fountain pens. While half-moon types are common, we sell it as a sheet type in a "semi-size that fits nicely in an A5 notebook." Since the Japanese paper is cut into sheets, it doesn't leave marks when sandwiched, and it's convenient as a bookmark even for those who don't usually use blotting paper. Also, the material uses bamboo, and it is neutral paper convenient for preservation. Thank you for viewing.