Vouchers are categorised according to the licence level examination they access.
Mock (practice) exams are available for the two MPC subjects, all PPL(A) subjects, some PPL(H), some CPL subjects, BTK and some ATPL subjects.
Unused vouchers are not refundable. However they are transferrable, so you can give/sell unused voucher codes to your friends to use.
Not all subjects have examinations available yet, so check carefully before purchasing vouchers.
More subjects are coming soon.