So I purchased a pair of Etymotic ER4S earphones a few months ago. They are amazing. I will be making a detailed review sometime for them. Suffice to say, I accidentally washed all of my stock tips in the laundry (they were in a baggy together). They became warped and unusable.
So, I emailed Etymotic asking if they sold a pack of the stock set of tips for the ER4S. Instead of selling me a pack, they sent me one of each tip for free!
That's great customer service. They have also been very friendly and informative answering any questions I've had. I highly recommend the ER4S and the experience they provide when you purchase something from Etymotic.