The Gibraltar Hoop Guards do exactly what they say- protect your bass drum hoop! I've also found the help with any bass pedals that like to slip off the hoop whilst playing.
They are relatively durable- I had about nine months' usage from my first guard. My main gripe, however, is with the adhesive. This perishes quite quickly, losing it's stickiness completely. After about four months I had to resort to affixing the guard to my hoop with two small strips of gaffa tape. The adhesive sheet is also prone to peeling off along with the sticker cover.
Although annoying, this doesn't stop them from doing their job, and they're definitely worth the minimal cost to help reduce that dreaded hoop rash.