Debentures entitle the holder to purchase one ticket per debenture held for all RFU rugby union matches at Twickenham. For non-internationals (and certain internationals that are not expected to sell out), debenture holders may apply for more tickets than their debentures entitles them to.
Debenture holders are not guaranteed tickets for concerts or other non-rugby union events. If the RFU receives an allocation of tickets as the venue, part of that allocation will be offered to debenture holders. In the past, concert tickets have been offered to debenture holders on a first come, first served basis, four tickets per holder regardless of the number of debentures held, but that method of distribution is subject to change for each event.