In my case, the passenger side was the easiest fit & it snapped into place quickly. On the driver side, I had to work round a wiring harness and it was a bit of a challenge to get it to snap into place. I found that installing the where the harness was (on the left, closest to the driver door) and then fitting the right side worked. Once snapped into place they are a snug fit. Overall, very happy with the results. As far as "adhesion", mine did not come with any double-sided tape. Instead, they snapped into place onto the car's vent via tabs at either end of the cover. Seems like a good idea to me, especially having kids. Items tend to get dropped and sometimes kicked under the front seats...