These type things can harm you and your money as this is never been profitable I personally joined one in start and lost big amount so now I will suggest you never take any risk like this just keep bitcoins this is giving good profit right now and try to research and analysis more instead of taking risk like this
Some interesting ideas on how to double your BTCs are also written in this thread:
https://bitcointalk.org/index.php?topic=2331627.0;topicseenThere is always big risk, no gain without risk.