So a few months back I gave up on the white bumpers for my white iPhone 4 because no matter how clean I kept my hands and pockets lint free they kept yellowing/greening/dirtying over time. The threads recommended magic erasers, watered down bleach, boiling it, baking soda, whitening toothpaste, tilex, etc, you name it. I tried them all and some worked okay, but most were abrasive and didnt quite get rid of the yellowing completely and none of them worked well enough to satisfy my super white iPhone fetish until tonight when I was cleaning my Movado, it hit me, JEWELERY CLEANER!!!!! You know that generic clearish-red fluid cleaner all jewelers sell/give away for stainless steel, gold, sterling silver, watches, etc. so I used a cue tip and dipped it in the solution and rubbed down all my white Apple bumpers and SW box bumpers and WOW. Perfect! Good as new! Totally got rid of the yellowing and brownish dirty look. Just thought I'd let u all know since many ppl complained about it before when I did. Sure beats spending $29 on a new bumper or shipping on the cheaper ones.