What is the maximum RAM capacity and type for the Dell OptiPlex 3040 Micro?

The Dell OptiPlex 3040 Micro supports up to 16GB using two DDR3L SO-DIMMs. You must use the low-voltage 1.35V DDR3L — standard DDR3 won’t work and can damage the board. Stick to 8GB modules rated PC3L-12800 or similar.