I prefer one that's a tight fit. It may be like mounting a tire but at least it'll stay in place. The last one I had was always sliding out of symmetry(had the rubber grips at 10:00 and 2:00).

The leather slip on cover I use now is excellent. Comfy, doesn't slip or get hot and sticky. Forget the brand.

 

Picked another one up yesterday afternoon, and left it on the dash for about 2 hours... Took a bit of tugging, but it did slip on after that! And wow, what a difference it makes having a thicker wheel grip!! Totally changes the driving feel of the truck, almost more relaxing?! Could be the best $10 I've spent on this truck so far