It's plastic and rounded at the end. I've never scratched anythign in the least bit with a plastic razor blade. You can fid them at body shops too I think. I can't remember where we got the ones I have at home from.
If you really can't get the adhesive off, now... this is going to be a little scary sounding maybe... but I know how to get it off. Make sure the car is in the shade and has already been washed. Bring out a bowl from the kitchen (just a small one that's not plastic so it doesn't keep the flavor of this stuff). Now take brake cleaner or carb cleaner and spray it into the bowl. You only need a tiny puddle of it. Dip a cotton swap (for smaller spaces) or a cotton rag into the cleaner and scrub away. I keep a hose nearby so I can flush the area too. It will take it right off. Just again, make sure you flush the area well.