Because by law you have to inform your passengers 

DASH CAMERA STICKER :

 " Dash cam recording "

• 
  100% brand new, and very good quality,  universal fitment to all the vehicles .Easy to install, just peel and paste.
  
  Material:High quality PVC  environmental protection material,waterproof sunscreen,not fade
  
  
  
• Size: 5.5" x 1.5" inch ,  14 X 5cm
• Shape: Rectangle
• Color: Yellow
• Quantity: 2 STICKERS
• Paper: White Vinyl Sticker - High Gloss
• Also includes: 1 seatbelt sticker (2.5 x 2.5 inch)
• Quick (2-8 days) shipping with USPS