For starters, the upgrade kit arrived within a week of placing my order (I'm from the Netherlands)! Great stuff.
Second, this product is the best! Only after ordering did I realize that my version of the Hario Skerton (the Skerton Plus) already HAD a stabilizer in it. Nevertheless, this still left a lot of play while grinding, and the Blue Horse one turned out to be a much tighter fit. Therefore, I heartily recommend this upgrade kit to owners of even the Plus version of the Skerton. Its MUCH better than the OEM part. Buy with confidence!