Product review (3 stars): Doesn't allow for proper heat distribution
These come over sized, and you'll have to cut them with scissors for a custom fit.
I was afraid they might slip out of place when sliding cookie sheets or pans over them, but they stayed in place surprisingly well.
I thought these would be made to go on the floor of my oven, and catch any drips that tend to accumulate there. Unfortunately, that is not the case. The instructions specifically tell you not to put these on the bottom of an electric oven. (It would probably be fine to do so in a convection oven.) Rather, you are supposed to put these on the racks themselves. Doing so prevented the heat from distributing properly, as they blocked the heat  between the racks, and my food would not bake properly. I ended up removing them after a couple of days.
*This product was provided for testing and reporting purposes. I have received no compensation, nor am I obligated to leave a favorable review.