The Ultra tier is only available as an annual subscription.
Current DC UNIVERSE INFINITE subscribers can upgrade their monthly and annual subscriptions to Ultra.
If you originally purchased your subscription through the DCUI website and would like to upgrade, please read here.
If you purchased your subscription through iTunes or Google Play and would like to upgrade, please read here.
Otherwise, members who remain on their current monthly or annual subscription will continue to receive new comics six months after they are available at comic shops.