I had one Blu-Ray movie I downloaded, A Micheal jackson concert - 29 Gigs.
The container format for Blu-ray is BDAV MPEG-2 transport stream.
The file had extension .m2ts. I had to install PowerDVD 12(With Blu-Ray support) to play the movie.
A Blu-Ray disc is up to 25 Gigs on one side. Largest movie I ever had...