Product Number: base 00001 Handmade genuine leather (cowhide) Saikol Special Cover Model The Saikol whistle from Sanwa Seisakusho, which produces a sound even when blown lightly. This "science whistle" is a disaster prevention and crime prevention whistle that emits a 3150Hz sound, the easiest frequency for the human ear to hear. Because many people are embarrassed to carry just the science whistle, we are selling it as a special set with a special genuine leather cover m(_ _)m This is a special design for the Saikol, so you can change the color variations by purchasing different colored Saikols (*^^*) You can coordinate it in various ways, such as on your bag or belt loop. This product is a 520BASE (Gonimaru Base) original product m(_ _)m ※ This is not a project of Sanwa Seisakusho. I fell in love with this whistle, which is a very wonderful product, and designed and manufactured it myself because I wanted it in a style I liked (*^^*) The number of people who want it has been increasing on social media, so I will be listing it on Mercari m(_ _)m ※ Please note that this is the Mercari-exclusive selling price m(_ _)m - Model Name: Genuine Leather Whistle Cover with Saikol - Color: Blue - Material: Leather - Decoration: Turquoise decoration - Sound Frequency: 3150Hz Thank you for viewing.