Dumb question - what is the EV adapter?

I’m curious what the difference is between these two drives:

I apologize but I looked everywhere and didn’t see anything about what the heck an EV adapter is. Why is the drive without them faster? Is there a benefit to having an ev adapter?

Thanks, and sorry for the dumb question.

The one without the ev adapters uses 2 more drives, meaning it leverages the speeds from those extra drives and it is faster and has larger capacity.

The ev bay adapters are empty cartridge bays that allow for our ev mobile drives to be slotted in.