1.Use high-quality materials. -SRO4 ultrasonic ranging module, stable measurement, range up to 4 meters. 2.The ultrasonic distance measuring instrument of single chip microcomputer is designed with single chip microcomputer+-SR04 ultrasonic sensor+Nixie tube+button+buzzer. 3.The alarm distance can be set. After pressing the setting button, you can the plus or minus keys to modify the alarm distance, and it has the function of saving after power failure. 4.When the measured distance is less than the set distance, the buzzer alarm. Can be used as a car reversing radar, and the alarm distance can be set by pressing a button. 5.The characteristics of this design: wide measurement range, stability, and very convenient operation. It can be used when powered on. Working voltage: DC 5V (DC interface) Note: This product is a DIY kit, not a final product, you need to solder it yourself! This soldering project requires basic electronic knowledge and hands-on ability. 3xAA batteries are not included, you need to prepare them yourself Colour:Blue&Transparent&Black Material:PCB+components+acrylic Package Contents: 1 x Ultrasonic rangefinder DIY kit (DIY kit, not a final product, you need to solder it yourself!) Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.