10. Inventories

Inventories as of as of December 31, 2014 and 2013 consist of the following:

December 31, 2014 December 31, 2013
Crude oil and gas 22,619 20,328
Petroleum products and petrochemicals 41,787 44,836
Materials and supplies 34,422 21,280
Other 7,243 6,359
Less inventory provision (3,413) (2,580)
Total inventory 102,658 90,223

As part of the management of crude inventory the Group may enter transactions to buy and sell crude oil from the same counterparty. Such transactions are referred to as buy / sell transactions and are undertaken in order to reduce transportation costs or to obtain alternate quality grades of crude oil. The total value of buy / sell transactions undertaken for the period ended December 31 is as follows:

2014 2013
Buy / sell crude oil transactions for the period ended December 31 41 450 64 281