21 Outdoor LCD Backpack Walking Billboard Android Advertising water resistant Billboard with Horizontal and Vertical Backs ItemPanel typeTFT-LCDLCD PanelSize18",21",24"Aspect ratio16:9Touch typeNo touchResolution1920*1080Brightness300 nits to 1500nitsContrast ratio1100:1Enclosuremetal casecold rolled metallic +Backpack HardwareprocessorRK3288 ,1 speakerNetworkBuilt-in WiFi&4GFeatureAuto-play adsI/O InterfacesUSB, HD, WIFI, 3G/4G SoftwareOSAndroid 11APPmulti-screen adsLanguageEnglish MediaVideo FormatSupport MPEG1/MPEG2/MPEG4/TS/FLV/MP3Image FormatSupport JPG/JPEG/BMP/PNG/GIF