What can I use to convert 25gb .iso to a mkv of size choosing?

[dgrams]

Is there any way to transfer my 25gb iso down to say a 15GB .mkv (or even compress the 25GB iso down to a size of my choosing, say 15GB?)

If so, what tools are there?
Lets start with free ones and go from there.

[GregiBoy]

Not appropriate to ask here for free programs as the Ripper module will already do this.

[90312]

You can do what you want in DVDFab, select MKV and advanced settings and in video quality select customized then slide the bits/pixel button over until the file size is 15000MB and BOOM!