i-94 duration for B2 visa?

Hi,

My parents got the B2 visa to visit us and I am working on buying the airline tickets for them.  The term for the price I want to pay will not allow changes to the dates.  So, I need to know how long of the valid staying (stamped in their I-94 when they go through US custom) in US for B2 visa holders?  Still ~ half year?  My parents have not been in US for 2 years, so I don't know the current situation.

Thanks and have a nice weekend!