Memory Replacement Voltage Question

I want to replace the RAM in my MBP model A1278 (early 2011). Wondering if there was a certain voltage that the RAM needs to be. When looking to purchase I see that there are options in voltage that are 1.35V or 1.5V. Do both voltages work in my version of the MBP or should I be careful and purchase only one of the above options. Thank you.