Best Galaxy S21 Ultra thin cases in 2021: slim yet protective! These are some of the best thin cases you can currently find to keep your brand new Samsung Galaxy S21 Ultra safe from falls and scratches 3 minute read The Samsung Galaxy S21 Ultra is the largest and most powerful model of the latest Galaxy S21 series. Unfortunately, it is also the most fragile, as it is the only device to feature glass on both sides of its aluminum frame. So, you may want to consider getting a new case to protect this $1,200 investment. You also have to remember that the Samsung Galaxy S21 Ultra already comes with a large footprint, so your best choice could be a new thin case that will give you protection from falls and scratches without having to add extra bulk.