Apple Macbook Pro 13.3" 2.5 GHz Core i5, 500GB HDD, 4GB DDR3L RAM - MD101LL/A (Non-Retail Packaging) - Walmart.com
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
Apple 13.3-inch MacBook Pro Laptop, Intel Core i5, 4GB RAM, Mac OS, 500GB HDD, Bundle Includes: Black Case, Bluetooth Headset, Wireless Mouse - Silver (Certified Refurbished) - Walmart.com
MacBook Pro 13" Unibody Early 2011 RAM Replacement - iFixit Repair Guide
Memory RAM Upgrades for MacBook Pro (2012 - Late 2016)
A-Tech 16GB Kit (2x8GB) RAM for Apple MacBook Pro (Mid 2012), iMac (Late 2012, Early/Late 2013, Late 2014, Mid 2015), Mac Mini (Late 2012) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
16GB Memory Upgrade for MacBook Pro, iMac, and Mac mini
How to upgrade the RAM of a MacBook Pro to 16GB - Quora