Needs to be more sticky for the outside of the vehicles!

I love the look and feel of the bumper stickers!! The quality really impressed me!! Since this was my first order! Until I have gotten complaints that the bumper sticker came off while driving down the road. I was like totally shocked! I haven't had the time to call stickermule to let them know, But I am sure they will check into it. Otherwise I was please on how quick they arrived. I would buy from again for sure. I just hope they fix this problem with this product