Shitajiki ruler compatible with planners Lite Mini Diary - B6 Slim of the Japanese brand Kokuyo.
Besides of being a ruler, it can be used as a hard surface to write in.
Kokuyo is a Japanese brand that was founded in 1905. Initially, this brand made book covers, however throughout the years, the founders explored new business and they started producing and making their own stationery products. Among the most popular products made by Kokuyo, there are the vocabulary cards, which are used by students from all around the word to learn and write kanji and vocabulary. The headquarters of Kokuyo are located in Osaka.