All types of doubler, trippler, multipliers are just scam and there is not even one site that is paying for more than month (many stop paying even in first day if amount is bigger). No need to believe in any of their claims, stay away is only suggestion everybody will give you.
Yup sometimes what they promised are not in line with what is happening. Because the system as they do is less appropriate for trusted, because to be able to duplicate the bitcoin in cooperation of all the people that need a track record and proven in the past or can it be said that we can't get a good profit if they only give a bullshit