Ron Matusalem Gran Reserva 15 is not a fifteen year old rum as many people believe, rather it is aged according to what the company calls a solera aging process which is described on their website as follows:

The Solera aging system is a cascading process where slightly younger rums are blended with slightly older rums. Stored in oak casks, the aged rum are stacked in different levels. The oldest distilled rum is housed on the lowest levels. Newer rums are put into the higher levels so that the youngest is on top. As the rum is pulled from the lowest Solera barrels for bottling, it is replaced with rum from the levels just above. This process is repeated with the remaining levels, though no more than one-third of each cask can be drawn off every three months. This marrying of old and new softens the fiery younger rum and provides it with a refined smoothness and flavor not found in ordinary rums. A 15-year Solera or a 10-year Solera is an average of the blended years. Our Matusalem rums are Solera blended and are a blend of aged rums that average a year’s designation.