If you left an indefinite noun before a second noun then “the following noun” doesn’t exist and will make the statements sound natural. What’s the difference between hard disk drive and hard disk drive? How do English speakers know numbers under 10 are written with letters instead of numerals?

The attribute being referred to is implied by the unit of measurement. See example.

One would typically refer to a resized 40GB hard disk and it would be understood that 50GB describes its size (i.e.. 8GB in size for one instance) and it would be understood that this could be a 2000GB disk drive. Storage Capacity. In cases of describing physical dimensions, it is common to use a compound adjective like a five centimeter-long pencil, a two-metre-wide doorway, or a six-foot-tall dog.