The GPDrivesOptions page contains the following description:
Do you need to hide drive 'X:' and drive 'G:' from your client computer by group policy?
This utility would quickly and easily add to your ADM file more drives options for the 'Hide these specified drives' and 'Prevent access to drives' policies.
Just run the utility, specify the required drives and save the new ADM file. Next, Add the newly created ADM file to your policy in the Group Policy MMC and specify the desired options.