Cannot find any specs on what type, size, dimension, brand etc. hard drive I can get and fit into the empty WWAN slot on my W520-4270CTO laptop. Spoke to 5 people at Lenovo Tech support and they could not tell me anything. They had no idea. DOes a regular 500-1T/7200RPM drive fit, or do you need an SSD only for the space? (That's like 6X the $$$).