I have been intersted in these before as well. I never purchased one, because there is a serious lack of information on them, and I hated to take a gamble with my money. I did read one short review on a popular dealer's site, and the reviewer said that the spring tension was disapointing. I can't really help you, but if you do purchase one, please post your thoughts on its quality and whatnot. Because not many others have.