The Express 4k+ has an adhesive strip for mounting it, and it's supposed to be removable (like those picture hanging things that have a tab you pull to release them). I needed to take mine off for something, and the tab didn't release it. I pulled it out until I thought it was going to break, and it still didn't release the Roku. I wound up prying the thing off by hand, which was really difficult (the adhesive is really good). The adhesive strip stayed where it had been mounted, so after doing what I needed to, I just stuck the Roku back on. They need to go back to the drawing board on this.
