3M is a well known brand and reliable. Avery is also very good, as good as 3M, but not well known. A8 is Avery 8 year automotive grade vinyl. Make sure the vinyl is automotive grade, 2mil, and rated for at least 7 years.
3M also has some very thick, cheap, non automotive grade vinyl, so just because it says 3M doesn't mean it's going to last. I've had lots of vinyl stickers in 3M, but didn't stand the test of time. Check the grade before buying.