The MacBook Pro 15 2.6GHz quad-core Intel Core i7 can accept up to 16GB of memory with the 2 memory upgrade slots available
There are 2 memory upgrade options:
8GB ram upgrade (4GB X 2)
16GB ram upgrde (8GB x 2)
This specific model of MacBook Pro requires the use of DDR3 1600 Mhz sodimms.