Hi Steve. I used to have mirrors that were held on with a rubber strap, but on my last car one of the mirrors actually sheered off as I was strapping it on due to the force required. So when we changed the car last year for a Sharan, I also changed the towing mirrors, as they didn't fit too well. I went for the Milenco Aero Towing mirrors that clamp on. Once set for the car they are very easy to fit and remove and I'm very happy with them. They're not the cheapest, around