This is a Hinoki cypress wood board, approximately 10mm thick. It's slightly thinner to keep the price down. Hinoki is very durable and can be used for many years. I also offer a version made with a thicker board, closer to the actual thickness of a postal slot. Using that will reduce errors caused by angled insertion. I've included an eighth photo to show the difference in thickness between the boards. The photos are for size and shape reference. The item you will receive is of the same quality. This item was created out of a need I, as a Mercari user, felt would be useful. I'm confident you'll be satisfied. I've had nearly 1000 customers who have been happy with it. Hinoki has a pleasant aroma and is very soothing. Wood is flexible, strong, and becomes more refined with use, making it environmentally friendly. Above all, the texture of the wood is superb. I've received many comments saying people are surprised by how durable and pleasant to the touch it is. I've been using it for a long time myself. Unlike thin materials, it won't bend like a ruler. It's as sturdy as an actual postal slot, allowing you to check beforehand whether you can force a package in. I don't think there are any commercially available thickness measurement tools with this much thickness. If you would like measurement slits of other thicknesses (e.g., 1cm or 5cm), please contact me via the comments section of the order acceptance page. It may take a few days, but I will do my best to accommodate your requests. I will use recycled materials for packaging. If you purchase multiple items and they can be shipped together, I will reduce the price by the equivalent of the shipping cost. I may change the shipping method between Yu-Yu Mercari Bin and Raku-Raku Mercari Bin without notice. Thank you for your understanding. #TakawataHandmade #TakawataPackingScale #YuPacketPost4cm #YuPacketPost #ThicknessMeasurementRuler #ThicknessGaugeRuler #ThicknessMeasurementItem #ThicknessMeasurementGoods Yu-Packet Post Thickness Gauge Ruler 4cm Thickness Measurement Ruler Scale Yu-Packet Plus Measurement Ruler Mercari Shipping Mercari Scale Shipping Ruler Thickness Measurement Ruler Thickness Measurement Item Thickness Measurement Goods Thickness Measurement Scale