I got the plastic slide over myself and considering the best price i have found for the factory row mirrors was over $300, i think they are worth it. My instructions said to slide over te end of the mirror but i had trouble getting one tight. I found instructions for another truck make and they said to put the bottom on first and snap the top over and that works much better for me.
Only complaints i have is adjusting the mirrors correctly, mainly on passenger side, i can never seem to get it right. So i purchased a 2" round sticky mirror that swivels and that has helps if it isnot adjusted good. Also, the passenger mirror is not the "object may appear.." types and really seems magnified to the point you do not have a great top to bottom view as on the drivers side.
All in all i am happy with them for now, especially the drivers side. Maybe i will just buy the passenger factory tow mirror and leave the cipa on the driver's side. I am sure that will make for some great laughs
2011 Heritage Glenn 312QBUD