When it comes to PC storage, SSDs are definitely the sexy choice. However, their one drawback, aside from higher prices compared to their mechanical brethren, is smaller capacities. That’s the one area where mechanical disks still dominate, and Western Digital’s newest units only reinforce that fact.

The company announced two new additions to its “Green” line of consumer-oriented 3.5-inch hard drives. One has 5TB of space, while the other has 6TB of room for your stuff. Both drives will include a 64GB cache, along with the company’s IntelliPower energy-management tech. Western Digital claims that because of the line’s eco-friendly features, the drives run cooler, which enables them to last longer.

According to this official Western Digital document, their two new Green drives are the fastest in the whole series. The 6TB version transmits data at speeds of up to 175MB/s, while the 5TB model is slightly slower, shuttling data at a rate of 170MB/s. They’re also the most power-hungry of the bunch, sipping 5.3 watts when in use, 3.4 watts when idle, and 0.4 watts when sleeping or on standby.

Western Digital says that the 6TB drive can be used with its My Cloud, My Cloud EX2, My Cloud EX4, My Cloud Mirror, My Book, and My Book Duo storage devices, though it fails to mention whether the 5TB model will be compatible with those units as well. Along with the new Green drive, Western Digital also announced a bunch of Red drives, which are geared for use with NAS (Network Attached Storage) gear.

Western Digital has not revealed when these new Green drives will be available, or how much they’ll cost once they’re on the market. We looked around on Google, Newegg, and Amazon, and haven’t been able to find them, so it doesn’t appear that they’re available just yet. We imagine that they will be soon, though.